Youtube recently updated it's terms of service such that they can delete unprofitable accounts, and while this is probably about unprofitable uploaders, the wording allows them to delete the entire google account, and allows them to also delete unprofitable watchers, theoretically. Even if they're not doing it now, I'm still highly worried.

(Also google has a history of deleting google accounts for minor offences (in the sense of "stuff I can imagine me doing without noticing it was against TOS", like re-selling my pixel), so being dependent to them is a big issue.