They don't, It's just a better result for the users who get newer and better software, and a better result for the sellers who only have to support one version and get a consistent cash flow.
There are people running ancient MacOS versions, because that allows them to keep using professional firewire audio interfaces they have.
How would subscription model that breaks expensive hardware compatibility, breaks all your existing photo/video projects (aperture/final cut), or breaks compatibility with really expensive plugins needed for work be better for users?