They might be motivated by political views, fact checking, etc, but the subreddits I’ve seen discussing it (baseball, Iowa) are focusing on the fact that you need an account to see anything now. Screenshots from X would still be permitted; just not direct links due to the degree of interaction with the site required to view the material.

It’s sound reasoning, in my opinion. X either links you to an actual source or is a short post easily captured in a screenshot.