I think there are two points you haven't considered. First, for startups which take VC, a "modest exit" can mean that the founders get nothing. The range of outcomes where founders become fabulously wealthy but early employees do not is fairly narrow. Second, most founders start off by not taking a salary. Deciding to be an employee instead of founding your own startup means implicitly deciding to take more salary up…
(this is slightly off topic) I'm not crazy about how equity gets distribution in start-ups. Long story short, founders are compensated for work without salary. The problem is that stock should go to whoever contributes most to the company. Just because the founders work for free, doesn't mean they contribute the most critical work. Here is an extreme example to prove a point: I write a business plan and successfully…
that said, no one's stopping you from starting something and dishing out equity however you want :)