First, and probably most important, plastic horns do not add atmosphere. They simply add neutral volume. It's white noise. This isn't anything to do with the quality of the sound, but the monotony. It's just one sound. You'd have the same problem with bicycle bells, or a constant loop of Will Shatter's scream from "Sex Bomb."
The next time you watch a game from Azteca, try to tell the difference between horns blown in appreciation, and horns blown in derision. I put it to the jury that it cannot be done.
So it's easier to for players to tune out the noise. It really is. The same amount of energy and time used for plastic horns, if applied to genuine atmosphere, would turn your stadium into a crucible of passion. Even drums and percussion, which are theoretically neutral, can be manipulated and combined into something exciting. Plastic horns cannot. They never have been, they never will be.
Can you imagine anyone trying? It would sound like the Tusken Raider Chorus from "Family Guy." It would sound worse than those kazoo bands that used to be on Johnny Carson every once in a while.
So how did Galaxy fans get rid of them at the Home Depot Center? Because season ticket holders complained. There is a fairly big profit margin on selling a buck's worth of plastic for $5.00, so you have to fight fire with fire. Galaxy fans were fortunate in that the fan base willing to make an annual commitment held this issue dear to their heart. That's the section of the fan base that front office listen to - as is right and proper. But if the fans who make the financial commitment to the team don't speak up, then your job is going to be a lot harder. Good luck.
"But my kid likes them." Well, your kid would probably like crack, too. Why don't you buy your kid some crack? Huh? Why don't you drive down to Bob's House of Pizza and Crack, and tell the man "Hi, I'd like to buy some crack cocaine and give it to my child." You're a lousy parent, a terrible person, and I hate you.
Which brings me to the more emotional response to this issue: