Here, I see a difference between wealthy heroes like Batman and Iron Man on one hand, who value keeping their identity as businessmen separate from their superhero identity because of the perks that gives them, and the Angel on the other hand, who, by being 'out' as a mutant also tries to be a role model for mutants by showing that he can function and thrive in baseline human society.
I've always attributed the trend away from the secret ID to the runaway success of the X-Men in the 1970's. Following the X-Men's lead, interaction between superheroes came to dominate the comics, rather than interaction between the heroes and the real world. As the focus turned more and more to life within a community of superheroes, there was less and less attention to the "civilian side" of characters' lives--noone wanted to see Scott Summers working a day job, they wanted to see him hanging out with his fellow mutants (heck, did any of the X-Men really *have* a day job aside from helping run their school?).
In the old days, a character had to have a life outside of superheroics, but the norm, increasingly, was to characters whose lives were led almost exclusively as superheroes. More and more visibly inhuman characters were created, who could not feasibly live a civilian life. With no panel time to devote to the "secret identity", the conceit fell out of fashion.
"We're Santa's elves, and we're here to tell you about ourselves!"--Summer and Eve
Glad to see her time in college didn't go to waste on the job market! (This was before the 1970s and the direction X-Men took that MWGallagher speaks of, though. It was always sort of implied that the students at Xavier's School kind of just live off the funds of Xavier and later Angel's as well.)
Scott was also a pilot for his grandfather's airline, but that was when he wasn't an active X-Man.
But, of course, today's audiences have no interest in that kind of variety.
I'm not a fan of the secret identity trope because it inevitably leads to more retreading of cliched turf. "My love interest can never know who I really am so it is ruining our relationship!" "My friends and family are always angry at me for being a flake, if only they knew my secret!" Crap like that gets old fast. Thats why it was so refreshing to me when Tony told the press he was Iron Man at the end of the movie, it meant we would be able to avoid the secret identity drama. It's much more interesting when they don't rely on that for plots. Daredevil hasn't had a secret identity for 10 years and seeing how he struggles with having his genie let out of its bottle is more interesting than seeing him bitch and moan about how his secret is tearing him apart.
And the obvious benefit - It provides an "in" for the audience and makes the lead character far more relateable - Especially in stories about alien beings like Superman or cultural outsiders like Wonder Woman.
I don't think they make much sense in terms of story or character logic but they're about the seven thousand, three hundred and forty eight goofiest thing in the average Marvel or DC comic. I don't think they work in Watchmen style superhero realism - Although th lead dude in Dan Clowes the Death Ray kind of had one, and that's the most effective realistic superhero story I've ever read.
(I'm not particularly a fan, although I really like Clowes' stuff in general. If I wanted realism, I wouldn't be reading superheroes. Obviously.)
But in general, I think they're a useful tool and some characters (Superman, Spider-Man) simply don't work without 'em.
Life looks better in black and white.
There are no bad ideas, only bad writers.
Mind you in the Golden Age the secret identity was overplayed. There was no good reason for a lot of the super-heroes to make a secret of their super-powers, but for the fact that Superman had a secret identity and all comic books were trying to copy the success of Superman--so they were going down the checklist of things that Superman had, hoping that this would recreate the winning formula.
For a character like Superman, the secret identity makes sense. Clark Kent is who we all are, Superman is what we cannot be. No one would believe me if I told them I could fly--that's crazy. Superman is too far out there to be real, which is the whole point.
Of course, one good thing that comes out of the secret identity is the costume--and the dramatic change into the costume. If these heroes have no secret identity, why are they making a production out of their disguise? One example here would be Hawkman. There's not a lot of reason for Carter Hall to disguise himself. Who is he protecting? Shiera Sanders? Given how they meet and their past life origins, it's kind of confusing why Carter ever tried to hide this from her and in the end they became partners and had no secrets between them. But the disguise allows Carter to wear that cool looking head gear (which often sat on top of his head and didn't hide his face at all).
And in retcon hindsight, the fact that almost all the JSA had secret identities allowed for the explanation of why they retired--because they were being compelled by the government to reveal their identities.
Almost all the JSA I say, because there was Johnny Thunder who had no secret identity--and no costume or mask either. There were other Golden Agers, like Aquaman and Sub-Mariner who didn't bother with secret identities. They were at work all the time.
When Ralph Dibny came along, a big deal was made out of the fact that he had revealed his secret identity to the world, but he wasn't the first.
Coming from a working class family--my father was a postman--I identified with most of the DC heroes because they approached their work like it was a real job. They went on patrol, they put on their uniform when they went to work and they took it off when they were done, they may have even had a punch clock so they could log their hours.
Clark Kent's job problems--he has to be in his business suit and his union suit at the same time--is the stuff of nightmares. I still have those kind of dreams. I find myself working at two different jobs, sometimes in two different cities, trying to fool both my bosses, in a panic that I won't be able to juggle both shifts.
Even Bruce Wayne, despite his wealth, approached his duty like a blue collar worker, keeping to a schedule, doing his nightly patrol, calling in at the Commissioner's office, responding to the Bat-signal and the Bat-phone, keeping records of his work. Bruce had a solid work ethic and proved that he belonged with the toiling masses and not in an ivory tower.
It made sense that all these DC heroes worked together. That's what you do when you have a job. You work with your co-workers. If you have a disagreement, you don't get into a fight on the floor. Maybe you go to human resources or your union rep and try to work it out. But a good worker is dedicated to the job and that's the main focus. Let's get this job done and then we can go home to our families.
Ralph Dibny was an exception. He never seemed to approach this as a job. He was one of those who doesn't punch a clock. His interest in crime solving is purely entertainment. He therefore doesn't need to make a separation between work life and home life--it's all one to him, even if that frustrates his wife sometimes.
For me, there was always something about this guy in a blue suit & glasses & knowing that he was Superman. Comics are so grounded today. I mean having so many Marvel heroes connected with a government agency makes sense but just doesn't appeal to me. I guess I miss secret identities.
Astro City deals with secret-identity issues along with all the other super-hero tropes, and does all of them really well. The date between Samaritan and Winged Victory is particularly memorable.