No matter how many people repeat this silliness, it isn't any less idiotic to compare to sporting arenas or theaters.
The difference is, Disney markets itself as a "one stop" destination who does everything they can to keep you on their property from the moment you arrive in Orlando to the moment you leave. That means 3 meals a day, every thing you ingest for a week.
At the venues people try to compare it to, people aren't feeding families substantial meals because they are only there for a few hours.
So yeah, I'm sure it's kind of shocking for a family of 4 or 5 to budget $40+ for a few water breaks every day, especially since most places don't advertise that you can ask for free ice water and I doubt most guests know about it. If they did, Disney would stop doing it...