Yea, of course it you update it once in 10 years it's a huge chore.
But if you have an app that people actually pay money for, I think it's bad business to not spend the few hours a year to update it to the latest XCode.
And if you don't care, just delist it from the store so people don't buy your abandonware.
These apps worked fine, and were for specific types of measurements. They weren’t broken, they were finished. Apple just pulled the rug. Actually, everyone benefits except the consumers when this happens, because push comes to shove, they will just release a new one with the same price or as a SAAS.
I totally see the benefit of windows in these situations.
The vast majority of 10+ year old apps wouldn't compile with modern xcode, and even if they did they won't meet the stores requirements anymore.
For a small app with a small userbase, the maintainance cost isnt worth it.