Real answer is likely that we're so inundated with apps being a solution that most common people wouldn't even think to use the website. Most people aren't tech literate enough to know that their computer is still on, even when the screen goes black from inactivity. Same for phones. For this majority, the solution they're presented with of the Microsoft Store is their go-to, and they don't even know what an Operating System is.

I feel compelled to link this comic page here, even if most of us aren't experts. I think it still applies: https://xkcd.com/2501/