They are "serious" pictures, typically taken from the front and looking very professional. They are wearing at least a shirt, avoiding hoodies or similar casual clothes. They transmit "professionalism".
I lack this. It's not that I cannot wear shirts or similar clothing; it's just that I don't want to transmit "professionalism" merely through my profile picture. The problem I see is that if your profile/CV has a less-than-adequate picture, it's likely it will be rejected.
This probably doesn't apply to FAANG companies (the best counterexample is probably Peter Norvig and his hawaiian shirts: https://en.wikipedia.org/wiki/Peter_Norvig)
Certainly there are some patterns to be found, and many people in upper management (moreso outside tech) take the "good headshot" approach. That's just the commonly accepted path and checks the box.
I think it's fine to show more creativity. Alternatively, you just play the game and move on, expressing yourself in other ways.