My guess is that this data is actually used for network analytics by the carriers and to determine if the device connecting to the tower should switch to another one.

This data is vital for a mobile carrier to make sure to have a good signal coverage under all the possible conditions.

It's just a guess since I've seen similar data being analyzed in a previous telco I worked at, but I don't know their exact source. The goal there was to improve the network quality. I guess you can do the same w/o GPS, but triangulation with cell towers is very coarse.

Phones are jammed full of features that get disabled or enabled on a per carrier and per country basis.

Most of those features are not user visible and are compatibility hacks - ie. "use lower profile in video calls if country = FR".

I’d imagine that the carrier will agree not to use any data they do receive for anything but a handful of purposes, but I suppose that depends on the extent of the technical solution.