JetBrains products might be unusual in that the IDE is all about integrating lots of constantly changing external tools and therefore needs constant updates, so it's well-suited for a subscription model.

And for many people an IDE is something they can spend 5-10 hours a day in. I own a fair chunk of the Omni apps, but even doing the diagrams for my thesis I didn’t spent anywhere near that much time in Omnigraffle. The incremental cost of all of the subscriptions every month, in perpetuity makes the marginal choice to get another one (eg 1Password) tricky.