It's largely an artifact of the cloud dependency of mobile apps in particular. Every app has a bill someone must pay and a server or other cloud presence someone must maintain, patch, etc.
App stores also contribute in that an app without a dev account ceases to exist and can't be easily installed by anyone. So if the maintainer goes away so does the app.
In the PC era software could live forever. Even closed source PC apps can still easily be run today on emulators.
Yeah, cloud, app stores and breaking platform APIs. I know people who still use ATnotes on their Windows 7 machines, despite the fact that it was discontinued more than a decade ago.
Still, PC era shareware (the equivalent to these small apps made by a couple developers) wasn't immune to cloud dependency, particularly when they had online license validation mechanisms.
You could always crack those if need be (at least if it was even a remotely popular application). And even if for some reason you couldn't, at least you had the files locally.
App stores also contribute in that an app without a dev account ceases to exist and can't be easily installed by anyone. So if the maintainer goes away so does the app.
In the PC era software could live forever. Even closed source PC apps can still easily be run today on emulators.