1. Due to demands from marketing/sales, the supplier tends to increase versions for what is actually a minor feature, just to justify a new payment.
2. A subscription process is the most honest way of selling software. Jetbrains is a good example of this, where you get to keep your "fallback" version when you stop the subscription.
3. You often have to wait a long time for the next release, if you don't want to register in an "early access" program with versions that break constantly (basically providing free test resources).
4. You need to justify the new version to your boss, so that you can get it covered and start the approval process higher up in the hierarchy.
5. Approval processes in large Enterprises are often complex and time consuming. This not only applies to approving the payment, but often need to involve central IT. With a subscription model, this is only done once.