Interesting question, why we can't just tune out other people and/or their conversation? Some people (I was one) have too much conversation with themselves/going on in their own head and sounds like others pay too much attention to what's "out there". I guess nowadays I'd try to catch myself being annoyed and then shrug and think, "there I go again, focusing on other people instead of the game/task I'm doing".

Were you at the game by yourself? Did you initiate going to and/or want to be at the game? What were the people behind you yapping about? Did you think of telling them to keep it down and/or feel you could not (in my case because I was angry and would "kill" them if I so much as turned around to glare at them :-)