It's essentially the same model used by other editors like the Jetbrains suite, but unlike Jetbrains, updates to Sublime Text (and Merge) are few and usually don't contain much other than bugfixes.
I've faithfully purchased Sublime Text licenses since the initial versions (switched over from Textmate), but as my ST4 license recently expired, it has forced me to review just what i get for the money i pay.
ST was excellent when it first arrived, and it's still one of the fastest loading editors out there, but pretty much every other editor has more or less caught up, including free ones like Zed and VSCode, making a recurring cost harder to justify.