they're working on the ad tech business and other business-related systems involved including internal tools.
and all the other platform engineering shit under the hood that makes much of the web scaleable... and lots of it is open source and contributed to by various engineers from these companies.
end of the day, these are businesses. they're not charities or whatever casual shit.
nobody is stopping you from building a competing product that's lean or whatever.
why don't you do something like that? i'm sure you're a genius.