In the past (and even today) some servers didn’t enable tcp window scaling, which limited you to a couple of megabit in say a 100ms distance download, not because of any conscious blocking, but because you couldn’t have more than 64kbytes in flight at any one time.

This was mostly fixed a mover 20 years ago when window scaling became default, but companies like signiant actually had demos where they deliberately turned off window scaling to show how their proprietary file transfer formats were so much faster.