An app would be nice but I've never had issues using the site on mobile. I just switch it to desktop view and everything is as it normally is just a little small. This is a free site that runs on ad revenue and premium subscriptions, despite the fact that an app certainly would increase the number of regular users on the site it would need to be financially beneficial for it to be worth their while. It's not like they can just ask Bill the IT guy to whip up a nice mobile app over the weekend, this stuff takes time and money, and they would have to believe that it was going to money well spent.