Yeah, they do, but an actually fair to all sides model is that of one-time sales coupled with optional paid-for updates.
It's worse in many ways too - it's a lot harder to gauge interest as the developer to understand how well any update will sell, and if the updates "stack", then a user only pays for the newest update to get all older features free. It's also worse from a cashflow perspective for the developer (but better for consumer) since they have to pre-build the update before any chance of getting paid for it.
If I buy a product and like it as-is then I don't necessarily want it to change over time.
Buy once is better, buy once with optional updates or periodic version releases is better still.
And generally speaking there is a lot of options that are excellent for developers but complete shit for the users. That's obvious, but it's also off the point in the context of fairness.