Typically when you buy a product with a perpetual license it doesn't include support, maintenance or upgrades. Think of Microsoft and no one runs windows 3.1 or even XP because their newer products are worth the upgrade. Typically they'll provide security patch updates but not new versions.
Other things like Plex lifetime deals are there because they either want the money on their books for investments or owners want to cash out. It also works kinda like a reverse ponzi scheme where they're relying on new sales to provide support for the existing sales.