If their websites were already mobile-friendly and responsive, there is only little benefit from developing mobile apps. In other words, it's pointless
Then I don't get it at all
I mean why would anyone (i.e. not just casinos) want to have a mobile app if they could just go with website optimization making it mobile-friendly, more responsive, etc? It would be a waste of time and effort if you can get everything from a mobile version of the site that you would get from a standalone app. Or maybe, it is exactly as you and I see it, i.e. it is indeed pointless, apart from obscure marketing purposes and that kind of thing? What's the catch?