I've sort of wondered this. I used to kill SNGs. But that was before UIGEA. Now...they seem a lot harder.
I've always been conservative in my play. And I intuitively "got" ICM and fold
equity before I had ever heard of them. For exampleI didn't want to risk busting out when someone else made the first move and went all-in. I wanted to control that. That mind set made SNGs very profitable for me.
Nowadays. Meh. Seems fairly break even. Everyone knows about ICM now. I think most SNGs are played by break even regs (and some bots). Hate to be cynical, but either I've gotten a lot worse or the games have changed. Maybe some of both.