I've bought Mailplane v3 for my Mac a few years back. The app did not get new features, only patches. New features came out with v4, which required another purchase. I didn't buy it because v3 is good enough, buying again is a psychological wall. If it was a subscription I'd be happily paying them and happily using the latest version.
They are not charging a subscription for you to be allowed to download Gitlab and self-host it.
The issue with a subscription for self-hosted or locally ran software is that you are obligated to pay an ongoing fee, without the provider being obligated to provide any service in return. Their terms do not require them to adhere to any release schedule or anything showing that by paying a subscription you're getting X. It's basically a recurring donation in hopes the software you already paid for gets an update.
Imagine if your OS required a subscription for your computer to be usable, even when the developer of your OS doesn't release any updates that benefit or affect you for months, if you don't keep paying your subscription you get locked out of all of your work for no reason other than some marketing douche thought it'd be a good way to squeeze a more regular revenue stream out of their existing customers?
First, you have to define the difference between "major" and "minor" version. Users expect major versions to have some significant improvements or new features. What this means is as a developer, you have incentive not to release minor features regularly, but instead batch them together so you can do a "major" release.
Second, the sales team now dictates the release cycle. More major releases means more money, but do it too frequently and the user base revolts. In many companies sales dictates the releases, but now if development is late it's messing with the company's cash flow and ability to continue to exist.
Third, the software can never be "done", because that means no more major releases. As a result, unless there is a sustainable stream of new users, you get feature and scope creep.
Subscriptions mean predictable revenue, and make the developer's incentive align with users: keeping users happy. This means keeping the product stable, making incremental improvements, and evolving with features that make sense.
Of course the beauty of the market is you should be able to find products sold both ways, and you can choose.