To quote good old Chester Karass (https://www.amazon.com/Business-Life-Dont-Deserve-Negotiate/...): you get what you negotiate. In an ideal world, people are compensated according to their contributions (and when hired, expected contributions.) This isn't a once-and-done thing, though - compensation (in the form of company ownership) gets adjusted all the time. The flat 10% is just a starting point (a typical CEO level of ownership in a start up, although this number varies quite a lot, due to aforementioned negotiation.) If a CEO screws up badly enough, they might get fired even before their stock vests.