The people who go to work for start-ups are usually young. There comes a certain time in life when you have a family that relies on you and you get old enough that you start to make plans for retirement.
That's when you get a real job at a very boring stable company and stop being delusional.
Well, that depends. I'm working in a startup and I'm in my 40's. Although it's a bit different than a typical startup, because it pays quite well compared to 95% of other offers in EU to live a very comfortable life in a not too expensive European city.
Yeah, the hours can be crazy but not too often. Yes, you're expected to give your best all the time but that's part of the fun. And the best part is the challenges are always interesting.
Maybe it makes it easier for me that I'm not at all interested in normal family life and never want to have kids.
That's when you get a real job at a very boring stable company and stop being delusional.