It would be very useful if you're always spending your time on here...
But really, it's not like you'll miss too much between visits to your computer. Using a phone Internet browser, like Safari, to browse this forum is a pain. Well, browsing is fine. Posting, replying, etc., however, is a hassle. Typing becomes super sluggish.
I always find other things to do when I'm out and about though. I converse with friends, play games, and do whatever other simple things I can do with my phone. I also bring my 2DS every where I go, which is much more time-killing than smart phone games.
Given the limited amount of people in this community, and the limited benefit of a 1st party browsing app, it's just not worth any time or effort to be made.