I still mourn the loss of Windows Phone (aka one of three mobile OS choices) because of the "app gap". Small developers wouldn't invest the time or money into porting their app to the small marketshare. Even worse though, large companies would let their apps flounder, if they had one at all; the Bank of America app was simply disabled rather than being updated.

If the PWA concept had caught on, users on all platforms would have an equally good UX, increasing user choice.