RSUs and bonuses, but yes, for the past decade for me about half of my compensation has been stock grants.

Working for small and privately held companies implies a major opportunity cost

I worked for a small private company for a number of years immediately post dot-bomb (not as a developer). It was a great job in many ways but not with respect to comp. It did lead to my current position which has been good. Everything has to be viewed in the context of career/life and alternative possibilities.

Google, Facebook, Amazon and Apple all have more than 100k employees, this is close to the full SF population, so doesn't look like "select few" to me.

These employees are not all software engineers getting paid out the yinyang with RSUs...