I’d guess correlation attacks rise above your average IP holder’s (and their attack dogs’) level of influence honestly. Would require cooperation with big tech to get a correlation and bank on you actually using big tech sites with personally identifiable information.
It’s mostly brand recognition/staying power. The Internet is a very scary place for normies, especially uncharted waters. Megacorps on the other hand bring a safe experience (lol) where they and their friends can hang out, chat, shop, consume etc.