The problem here is, that it shouldnt even be labeled as "purchase" (well, "buy" usually), but "rent". Purchasing a licence to rent the content is weasel wording around stuff that is well known and consumers expect it to work in a certain way (eg. buying a dvd or renting a dvd, where in the first case you actually own the dvd, and in the second, you know that they expect you to return it after some time). In every other business, "buy" means "buy", buy a dvd, buy a sandwich, buy a car, buy this, buy that... nowhere else are you expected to return the item (at least not without a refund, eg. in case of a recall).