I think you're right but for the wrong reason. Social media is insanely profitable, and when you anonymize that people wouldn't be as invested, so they want people in it personally and often.

I don't think it has to do with them compiling your information because it'd be easy for us to be outwardly anonymous on the web so no one you're interacting with has any idea who you are while still allowing those companies to track you in depth since they're behind the scenes. It's not like they need to know your real name to give you targeted ads.