If you can rent out a purchased copy (one for the courts, jurisdiction specific), then Steam/Microsoft/GOG/Humble could offer things as a subscription quite easily. If publishers are required to sell to them and not allowed to create roadblocks. Given the concurrent player counts for most games the subscription service wouldn't need to purchase many copies to allow almost-always access. The interesting games to consider are the 'always online' ones, where the software could be given away for free, because it is useless without access to the game servers. Which pretty much operates like a subscription ('lifetime' or monthly), and is expected to stop working one day.