I have a 40 something friend who started working there a few years a go. He has a family. He mostly went for stability, good pay, good benefits, predictable long term outlook. Not working insane hours. He loves it. Actually said he feels valued as an engineer.
I work in a country where engineers are paid like factory workers.. if FB offered me a job i would be happy to take it even they sold unapproved drugs.
Morally questioning a company with that kind of salary and benefits requires a position of incredible privilege.