> They are choosing to give Facebook info.

Yes, they do. That's is exactly the phenomena my comment addressed.

But the way you wrote that implies an improbable motivation or choice framing.

Perhaps their real motive/choice is to share with other people on the site.

It is called a network effect.

If (1) Facebook had been the surveillance/manipulation capital of the world from inception, (2) an equally inviting privacy protecting site took off at the same time, and (3) everyone chose Facebook over E2EE anyway, then sure, we could throw up our hands! Those silly users!

The term I have for when people discuss choices involving many-dimensional criteria, as if the choice involved just one or two selected dimensions, is "dimension blindness". It happens in a lot of heated discussions about phone choices too.