It could be perpetually licensed. Sure. But there's a business case to be made for patching out DRM very early in the product lifetime. The longer a product

It could be perpetually licensed. Sure. But there's a business case to be made for patching out DRM very early in the product lifetime. The longer a product is protected by DRM, the more likely the DRM is to be cracked, and that this crack could be applied to a new releases. It doesn't make sense to put a new game release at risk just to keep protecting some five year old game from piracy. If you're selling DRM, you want to disincentive publishers for using your protection for too long. And if the DRM is built in-house, you want it to keep functioning for a number of titles to amortize the cost of development.