In the classic version, Peter's walking down the street, encounters a burglar, and yeah, doesn't stick his neck out. But there it's more of a practical decision. He does what most passersby would do: not get involved. In Ultimate Spidey, Bendis had to have another character say that Peter could've tripped the burglar, because otherwise the story seems to fault Peter for not being proactive in stopping a criminal. And at best in this scenario, Peter simply comes off as lazy.
By contrast, the movie version has Peter make the conscious decision to let the burglar get away. It provides a better, more contained situation where he *should* get involved, and he doesn't. Peter lets the burglar go not out of laziness, but out of spite and anger. And he lets him go for reasons the audience can empathize with in the moment. He's not simply inactive; he makes a wrong ethical decision, for personal reasons. And Uncle Ben dies as a result. The lesson Peter learns isn't just to be more proactive and less lazy; it's to be a better man.
It also allows Peter a final moment with the dying Ben. Which isn't necessarily better, but it's a good emotional beat.But you're right, making the burglar a car jacker was SOOOOOOO much a better plot point.
Spoiler for "The Dark Knight Rises": Bane turns out to be Joe Chill's previously-unseen mugger friend who helped him escape after killing the Waynes.Which they then fucked up in the third movie, but that's the third movie.