I'm staying because I can't seem to leave. I'm too attached to my characters, but more so to the people that play the characters mine are attached to, and the stories we create together.
I stay because PS gives me something to write, even when I have horrid writer's block.
I stay because the people that are left in-game seem more optimistic now that most of the pessimists are either gone or lurking in the forums, and that gives even me, one of the said pessimists, some hope for it, and now that those same pessimists are gone and done crying that RP is dead, I'm seeing more roleplay.
I stay because my other game doesn't offer roleplay without you having to figure out which guilds, players, channels, addons, and locations to look into at what times in order to get around your fellow roleplayers' fear of griefers.
But it's mostly just the other players that have me staying.