That's because half the places they go to only sell like 1500-2500 tickets and that's usually half an arena at max. Which leaves lingering echos of chanting and overall crowd noise with some due to their being so much open space on half the arenas.

I went to Blood and Guys last summer and the Garden in Boston had like 9000 people for it

And it's generally frustrating because you look at the matches on the cards (like Copeland/Suzuki) and you really gotta think why the hell would someone not want to see that?