[octacat]

You have to use browser on mobile to enter them (no way to add an icon for them). + there are some other limitations. There was an article about that.

Web platform is pretty capable to be used for app development, it would save a lot of developer hours to not develop for 3 platforms.

[jeroenhd]

You can definitely add an icon for them, in both Android and iOS. I'm not sure about mobile Linux, as Firefox has dropped any interest in PWAs on desktop style browsers for some reason, but the most common operating systems let you install web apps straight from the browser.

[Borgz]

This is a problem that PWAs address