It has nothing to do with money.Wayyyyyyyyy more money could be made if they got rid of the chairs. Back in 1979 at a Who concert in Cincinatti, Ohio, a bunch of people got trampled in the rush to get to the stage when the doors to the venue were opened that evening. Standing room only was common practice up to that point. A band had a choice to use chairs if they so desired.But after that sad incident which really shook up all concert goers, it became law to ban that way of doing things and then there had to be chairs for the floor audiences. This is fact only in large arenas of like 4,000 or more.Not too sure on that number but I bet Homer McVie knows.

I do think a ga section in the front area would be cool.
I've seen Lady Gaga, Black Eyed Peas, Nickelback, Foo Fighters etc which all had floor as general admission and these venues were pretty big at least 12k and up. Its always a good time but sometimes you cant see sh*t!