FAANG doesn't need to use cloud either. Notably, Facebook doesn't (and, a bunch of stuff at Amazon was still not on cloud until _long_ after AWS was invented).
Sure - not everything at these companies needs to be on the cloud. But when you're dealing with sensitive information, you don't want people rolling their own infrastructure.
[0] https://press.aboutamazon.com/news-releases/news-release-det...