Adversaries don't always ask nicely. Sometimes they break in and silently take the data. These services centralize traffic flows and make it so that an adversary only needs to tap one or two circuits to get a full picture for all users of a service.

CIA is not stupid enough to break into a guarded data center in Switzerland or one of the less America friendly EU countries. They tell the NSA to look for security holes and spread narratives that only criminals use VPN hoping that a politician will notice and try to ban them, like what's happening in the UK.

Big tech services are less private than you think but almost every provider who cares about privacy is safer than you expect. Most of the people who work there are committed to their mission, and if they ever get a gag order someone will leak it in no time because they know exactly how to do it without exposing their identity.