I doubt they’ll ever actually do it, just threaten it constantly.

They’d rather have people without accounts, and/or using adblockers keep using the site. If they started actually cracking down, then it would create a significant pool of users who would use some other platform. They’d rather eat the losses of some people not viewing ads then push a significant amount of users to a potential competitor.

Much like how Microsoft hasn’t cracked down on unlicensed windows installs because it would push a significant amount of people to look for an alternative OS.