[oaiey]

That is neither regulation (just standard contract law) and IMHO a formality, because Amazon could have just formulated it differently: hey we terminate your contract, next offer: same thing with ads (vs. Hey we change the contract for profit).

This is not a structural victory just a badly executed change.

[tgsovlerkhgsel]

The reason they don't do that is inertia. "Hey we terminate your contract, here's a new worse one" will result in far fewer customers than "lol you got ads now".

Same with a lot of providers simply unilaterally raising prices. Entirely illegal, but they are mostly getting away with it.