We need to normalize anonymity online so Kiwi Farms wouldn't be able to kill people. The successful push for real identities destroyed the internet.
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.
They don't need your real name, but it helps. If Google knows to who you are everytime you sign into your Google account, that's easier than just relying on IP address to target those ads.
The old internet is dead and replaced with something worse.
But yes, pseudoanonymity is important.