One of the main reasons why PWA applications are not out in the market is due to commercial reasons. Those big companies wants to control the world market. PWA have been developed already with some glitches, but only if there is one who wants to challenge them, it is Yappadappadoo Store.
You are 101% right. Actually before the coming of these touch screen smart phones, when phones were just Nokia and already had internet, how were we able to open FRIENDSTER then when there was not Facebook and instagram yet? We used to open it in the web and it was ok then, no complains even when our phone screen was just small.