"I think it would be a smack into the face of the remaining states for her to step down at this point."

I agree.

You'll notice that Clinton has stopped criticizing Obama. That to me is the crucial sign that she has understood and accepted the race is over, and continuing to tear down the de facto nominee would only increase resentments against her as well as him.

She's staying in because at this point, it's better for everybody in the Democratic Party that all the states should get a chance to vote; because she doesn't want to look like she was forced out; and (I suspect) because she wants extra leverage with Obama when the time comes to figure out what her role will be in his campaign and, if he wins, in his administration.

Obama is fine with this because he wants his victory to look as legitimate as possible. He wants to be able to say that every vote was counted in every state and he came out the winner. That's why neither he nor his campaign is calling for Clinton to get out of the race. He'd also prefer to avoid the embarrassment of losing to a candidate who's already dropped out.