The core logic behind a rental (for physical goods) is reusability. Physical goods have a fixed cost of production per copy, so the price of selling it should cover that cost. Renting is expected to be cheaper than buying, because the object is returned to the renter which allows reusing it for new clients without expenses on another physical copy. I.e. most of the price in the rental case goes for the service of using it, and not for covering the cost of production.
With digital goods this whole premise doesn't apply. There is practically zero cost of producing another copy, so reusability is implicitly achieved with practically no expense by copying bits. And it also means there is no need to return the merchandise so it could be reused by others, since the merchant easily duplicates the merchandise practically for free. Therefore why would renting cost any different than buying? The whole concept of renting is illogical for digital goods. Therefore user can buy the digital merchandise for a (lower) price as paralleled by physical renting, while still retaining the ownership.
Netflix proponents claim, that they are charged per month to access anything, so in such context renting makes sense. But it still doesn't. They are charged for the service to stream the data. I.e. for convenience. It's cheap not because they need to return the merchandise so others could reuse it (as above). It's just cheap as is. There is completely no need to prevent users from retaining a copy once they watched it (i.e. which means buying). In order to it put in practical perspective, Netflix can be achieved without any DRM by selling each copy for some small price or / and charging a monthly fee for a convenience of streaming that data from the cloud while users could also keep those downloaded DRM-free copies all they want. I'd totally subscribe to such service. But I'd never subscribe to Netflix the way it is now because of DRM.