Except to improve services (ML training!), Advertising (We'll sell your data to advertisers!), and by government order (pick your favorite three letter agency.)
Alternatively: They'll just use your data anyway and not tell you about it. How is anyone going to prove their data was used as the source? It's like all the NDAs people sign when they join a company and they pinky promise not to use it at the next job where they land a big fat raise and promotion... suuure they aren't going to take what they've learned and improve upon it to try and get more promotions and raises in the future.
It can't be stopped.