Adding data caps reduces the total data volume, which in turn statistically reduces the average bandwidth used by all subscribers together (or whatever subset shares a connection).

I would like to know how you figure that load of horseshit. The average customer never even hits the data cap, so it’s not like it’s just cutting people off so others can get on.

It seems weird to ban consumer choice here.

What choice? Most of the country is stuck with whatever singular entity controls the network in your city. Very few places have any choice about what service they get.