W10M Why cant the browser make up for lack of apps?

[Williaml99]

On my surface pro if there was no app for XM radio or MLB.TV (example only) I could just use the browser. So why can't the mobile browser work in these cases? Why do we have to wait until full windows 10 on ARM comes to phone type devices. To make the browser work for some of these well liked applications would have made many of us very happy. I do know that there is store apps for the two I mentioned for PC but you get my drift i'm sure.

Thanks
Bill