Yep, there seems to be a great deal of magical thinking revolving around the idea of if you pay companies they wont keep on exploiting your data.

You still get ads on very expensive cable TV packages.

Your bank still data mines and sells off your purchase history, dispite a large monthly fee.

Do the user agreements in the two examples cited have any provisions that prohibit collecting data that will be exploited for advertising or marketing purposes?

What if the social network user agreement contained "privacy" provisions prohibiting collecting data if the user pays a fee but no such "privacy" provisions if the user pays nothing.

To do what? Facebook uses user data to, run Facebook, do research (train machine learning which uses de personalized data), and show ads. If they aren’t showing ads what other things are you expecting them to do that you find problematic.

  To do what?

In case you ever stopped paying; and because stopping displaying ads _and_ stopping tracking was more work than just stopping display.

They could just sell your profile to advertisers so you could get targeted ads on non-Facebook sites.

To get more money??