Ed,
That is likely the easiest question that has ever been asked here.
The ones of us who stay do it 1) because we need the site for whatever comes next, and/or 2) to help educate the ones we hope will get treated, get cured, and get their arses back on the road to what normality they may find.
The quantity of reason 1) folks is probably real high. I expect most 2's already qualified under 1). I do.
Everyone comes here with the hope of being here for a single post, a few days, maybe a few months at the most. I've never seen anyone sign a 12-month lease on day one.
A different way of saying what Tony said.