Even though I no longer read DC's new material, I am still sad to see all these characters go. Many of them were favorites of mine, and I sympathise greatly with their fans and fans of other characters who are now no longer part of DC's official continuity and probably will not be seen again in officially-sanctioned books (or, if they are, they will be so greatly changed they might as well be different characters).
This, however, leads one to the following questions: Why did DC reboot their whole universe? Couldn't they have only rebooted some of their series while still keeping those who weren't dead horses and still had good story potential in the previous continuity?
To answer the first question: DC wanted to attract new readers without them having to worry about decades of convoluted backstories.
And to answer the second: DC tried that before, and it just didn't work.