Statistically you are right that big tech currently provides the best expected value for a programmer, but in practice people's decisions aren't based on a single criteria. A lot of people find working for Google soul crushing and would happily take a $100k job that gives them more control and impact versus trying to navigate the path to promotion and relevance in a sea of stillborn products at Google.
I also agree founders want to get rich, I mean who doesn't? It's a nice fantasy. However if they don't have a deeper motivation to solve a problem for its own sake they will fail. If you're super smart and just want to get rich, the right move is to go into finance because you'll never cross the chasm of building something people actually want. Even the language you use to describe the premise indicates you don't really get what makes successful founders tick. Founders don't "work for a startup" and they don't need to be convinced—the whole point is these are people who have decided for one reason or another that they are passionate about building a company. You might think them fools because 25yo engineers are making $500k at FAANG and that is a high bar to clear for any startup (it is), but consider that all SWEs under 35 have never known a recession, and they may have come to believe that a programmer is inherently worth $500k even though this is just market rate given todays demand. If there is another dot-com style correction, a bunch of folks might find out real quick what the value of knowing how to make your own dollar is.