Directv can't just wave a magic wand and make the networks all buy 4K production trucks so they can produce multiple games in 4K. Not too long ago there was only 4K production truck in the whole country. By last fall I'm pretty sure there were two, because both Fox and NBC did 4K events but if you looked at the timing it was obvious Fox had just the one truck. Maybe someone else has a third.
Not to mention the networks would have to reserve a ton of C band transponder space, whatever special resources they need at their network broadcast site to handle incoming and outgoing 4K production, all the cameras needed at the stadiums and I'm sure many things I'm forgetting.
It isn't about what resources Directv has, they can only broadcast what networks make available to them.