because they dont get to work on facebook's main product and services. instead they work on stupid things like chatting service, facebook ads algorithm, etc. some of these have been around for over a decade already, nothing to innovate... literally just bug fixing or refactoring code. lots of tech people, especially tech talents want to work on things that have big impact / popularity. after a while you dont really give a **** about the pay anymore cause everywhere will pay you the same... and if u wanted more pay, might as well just go crypto companies lol they offer 150k annual to 300k annual with insane bonuses...

but people dont want cause some maybe dont believe in crypto, think it'll die 2 years down the road, or feel that crypto company techstack is useless for future prospect, etc.

if u are a fresh grad then definitely go for it, its a good resume booster for first job. from there u decide whether its worth staying for 2-3 years or not, also be aware that facebook has a 2 year cycle, meaning u need to show improvement every 2 years or else you're gone. im not sure if this is same for non-tech but it is for tech.