Do you have any actual examples of this happening?
I'm not saying there aren't people starting companies because they want to get rich, but I don't think it's happening in the droves that people make it seem like it is. I'm as pessimistic about the whole SV culture as they come, to the point of moving away in two weeks, but even I can't say I've met many, if any, people who seemed to be generally disinterested in what they were building, only doing it because they thought they could flip it.