Right now, it would be financial suicide for HBO to decouple from the likes of Comcast etc. Because that’s far too large a portion of their revenue and it wouldn’t all be replaced by an HBO Go subscription model.
And don’t think for a second that Dish and all the others would continue to pay as much and promote HBO as heavily as they do if they found HBO to be in direct competition with them.
HBO aren’t digging their heels in to be mean or to make people suffer (though you might think that the way some people carry on about it online). They’re doing it because they’re still trying to thread their way through a maze of licensing agreements, carriage agreements and accounting that would make it profitable.