I don't live in the area.
I've been to about 30 games at Texas Stadium and three so far at the new place.
I've also seen Dallas play in every city in the league other than St. Louis and Oakland.
From what I've noticed, in most cites, the crowd is made up of predominantly 20-40 year old males who who get nice and loaded before the game, and get very into things during it.
In Dallas, I've seen a lot of couples, families, small children, etc. Far less hardcore tailgating.
I will say though that Texas Stadium in the 90's, while not up there with some of the louder places in the league, was sufficiently loud. And at the right times (3rd down on defense) also.
Then somehow in ensuing years the fans decided the right time to let it rip was when the team was on offense in the red zone.
I don't know how to properly explain why all of that is, probably the corporate thing.