[enderm]

The main limitation is Apple. Progressive web apps are poorly supported by recent releases of iOS.

On Android, progressive web apps have way more support.

If I release a web app for Android, there are APIs I can use that prompt native installation prompts the user can see. The user understands my web app can be downloaded like an app from the app store can be downloaded.

On iOS, your web app just looks like a webpage to users. It is technically possible for users to "download" your web app by adding the webpage to their home screen, but this scenario is tedious. The webpage that the iOS user added to their home screen always opens in Safari, so it just feels like a bookmark to the user.

[ThePhysicist]

If you add an app to the home screen on iOS it will open without the normal Safari navigation/controls, so it definitely feels not like a simple bookmark. Also, the "tedious" process of adding an app to the home screen requires a total of three clicks on iOS (Share > Add To Home Screen > Confirm).

[ano88888]

3 clicks is more friction than you can imagine. It should be very visible (on the top or bottom bar) and definitely should be 1 click. It could mean 100 installs vs 100k installs differences.