I really think this move was precipitated by the Vegas move to get publicity off of the NFL. Last year Vegas was denied to advertise their "What happens in Vegas stays in Vegas" ads during the Super Bowl. This gave Vegas a great deal of publicity by being denied.
This year Vegas tried it again, probably knowing the answer would be no, just to get the free publicity again. The NFL had to get back somehow and I think that is the reason they made this move. Some board meeting of NFL execs went like this:
Chairman: "Those Vegas a-holes are making us look bad again. What can we do? Any ideas?"
Peon who wants to brown nose: "Well... they have these parties where they charge for admission. Maybe we can screw them on their parties."
Chairman: "That sounds like a possible plan. Look into that would you?"
My guess is that there are parties throughout the country that are charging admission fees, but Vegas was singled out by the NFL as retaliation.
Vegas Shut Out of Super Bowl ... Again