Because when I tried to open your page on my iPad using an acclaimed 3rd party browser (that I 'underpaid' for)...it crashed. And when I relaunched and attempted a gesture that I thought would get me back to your page it instead loaded 5 blank tabs. Generally my coffee doesn't explode and Brokeback Mountain was ... Ok. I finally got back to your site on my desktop, but generally the apps themselves are the best explanation for their cost. If you want a mildly theoretic explanation, usability and programing languages are probably where you should look... despite the sun never seeming to set on the behavioral economics empire...