Usability.
On my iPad for instance, when I want to visit Hacker News I open Safari and type "n", it gets autofilled, and I hit enter and I got there. Want to use my RSS reader? I type "1", it autofills, easy.
I have no trouble looking at a Desktop icon and interpreting it but for whatever reason all mobile app icons look the same to me. Although I have only two pages of mobile apps on my iPad (thank goddess!) I have several that have an icon based on an "N" and several that have an icon based on "H" and my Remote Desktop Protocol viewer is the same shade of orange as HN. Hard.
Mobile apps are frequently spyware, they frequently spam me with unwanted notifications, hide important functionaly behind hamburger menus. Just ask yourself, when you go to some site like Reddit and they put up a popup telling you to download the app because it is "better" -- do you really believe it will be better?