What OP said -- I regularly rotate among 6 streaming services and several of them do save everything if you restart the old account. In fact some of them used to have the option of putting the account on hold for a 3 month or 6 month period (probably for people traveling, having the service for guests, etc.)

Not all the streamers do save everything, as I've had watchlists lost. However given that they are in flux in terms of content and sometimes functionality, that may be more accidental than standard practice.