At least it was all "live" music and not the Kareoke rage that seems to be going on around here.
To the loud bands defense its really hard to play outside live for a large crowd if you don't have a sound man. You can never tell how the music travels and if the whole crowd can hear it clearly. Last week I went to see a Blues Band on an outside deck at a Marina. The first set was pretty mellow and not loud at all. I had to leave after the first set and meet my wife for dinner. When we got home a few hours later I could hear the band on my front porch and I live at least a mile from the marina deck !
Plus the fact that these bands are playing for a party/drink/dance situation, not a laid back dinner and listen to some back round music venue.

You never know and at least its only a few times a year.