A non-flatpak example is Electron. No one cares how big it is. It works.
I download huge games from Steam all the time and have never looked at the size of a game even a single time... in years. Disk space is still cheap on end users machines.
As long as the calculator works I do not care how much disk space it takes up.
As someone who's helped many friends/neighbors struggling with limited disk space (whether on desktop or Android), i don't think this is true at all. I mean, end-users are usually not conscious what a reasonable size is for an app and will often uninstall one app to install another one instead of complaining of app bloat. They're still very much suffering the problem and care for it.
A lot of people care, especially Linux users.
> Disk space is still cheap on end users machines.
Not cheap for everyone.