Audience behaviour tends to go down the pan (excuse the pan pun!) progressively, the less formal seating arrangements are: people are more likely to stay in their seats until a natural break if their are formal rows of chairs, though not all of them, as Johnny Jay has noted. "Cabaret style" with chairs and tables increases drink consumption and therefore trips to the loo. And as for "standing only" concerts, it seems it's the done thing to scream and shout at your neighbour/partner over the music: I sometimes wonder what people go for if not to listen!
Classcal music is not exempt: now it seems the fashion for the orchestra to play all their fancy twiddly bits in the pit while waiting for the concert to start. In my long-gone days of playing with an orchestra, all warm-ups had to be completed in the green room, apart from a final tune-up to the oboe's A once in the hall. And any production which is preceded by an overture, such as opera, operetta or musical theatre is now taken by some audience members to be background music for them to keep talking. Aaarrrgghh!