My phone doesn't always have an internet connection, or the internet connection can be flakey. Many of the apps I have on my phone work without that connection I find it valuable. It also has the side effect of not introducing random performance problems caused by IO which translates to a smoother more pleasant user experience and better battery life. Web pages really want a network connection for the most part. It creeps in at weird places in the design and that constraint leaks all over the place.