"They basically have to make a custom app for every platform/browser, when a single responsive website would have done the trick" ... well their are 2 things there: packaging add-ons for multiple platforms is not difficult. You create some kind of packaging wrapper code around a common codebase. It's building a codebase which works on many javascript and DOM engines that takes time and effort. So building a "responsive website" (that works on most browsers) is not much "easier" than packaging custom app for each browser.