For me personally being famous is a curse already, pile on top of that the endless fundraising, constant travel, the reality that you're a tiny cog in a huge party machine, and it's a recipe for only attracting the type who has a plan to parlay it into something else - a higher office, a lucrative career in lobbying, outright corruption, etc.
We're not going to get good government without addressing this issue, and we can't because of another issue, ad nauseam.