junior

I'm not speaking from the standpoint of an attendee, so my experience at them is a bit different.

Festivals are a great place for bands that "just get up there and play". I'm not knocking that approach. It's perfectly suitable for a lot of bands.
In recent history more bands are trying to achieve "their show" in a festival setting, and that is where the headaches start. At most festivals there is a default "house production" (the lights and sound) that everyone uses. Quite often it was designed with the promotors pocketbook in mind more than anything else. The light rig is usually either designed to look a lot bigger than it really is (like a puffer-fish) and not actually be all that useful, or it's just a very standard boring setup, or it's some crazy exotic thing that someone thought would look cool for the event. In any case, it makes it difficult to replicate the bands "vision". Often times the sound system suffers a similar fate.
So you have a touring show that took a fair amount of time to program and get it to the point where you are happy with it and you go to a festival and try to replicate it on completely wrong gear in a fraction of the time. You simply don't end up with the show you are trying to achieve. I've very rarely been pleasantly surprised with the results, and usually just try to forget it ever happened.
That might sound spoiled, but I just prefer the controlled environment of doing your own shows with your own stuff. Sometimes a festival will allow you to bring in all of your own equipment, or at least some of it. Even in a situation where you are just adding a backdrop, some video screens, and some floor lights you are usually met with some opposition from the organizers or you are met with a fair amount of grumbling for being a "difficult" act. In the case of Bonnaroo 2007, it worked out to where the festival agreed to not set up their lighting system until after Tool played, and we were also able to go in the night before and put our touring system in place. Had we played there Saturday that wouldn't have been the case. They were very accommodating. The sound company was the same one that Tool uses (Eight Day Sound), so the system was similar to the one we were touring with, and that made it a lot easier on the sound department.

It's not just my little part of the show that has to compromise. The sound guys usually have to deal with a local system engineer that won't let them have as much freedom as they have with their touring system, and they probably won't get enough time to tune the PA to their liking. On top of that, it might be suffering from budgetary concerns and just isn't up to snuff. Sound and lighting consoles have to be trekked out through the crowd before and after the show, usually through mud. Production and Tour Managers have to compromise their office, dressing room, and catering situations and a lot of the things they need to keep the show running smoothly. Security doesn't have their normal operating procedures for how the backstage area is run. Bus and truck parking is often fought over with other bands, and can end up being nowhere near the stage. Bathroom facilities are usually pretty bad, and good luck finding a shower. Guitar and drum technicians don't get the space they need, and have to "hurry up" with their set-up in between bands. This can be pretty stressful and lead to equipment failures and mistakes. If the guitar or bass rigs have a lot of technical particulars (pedals, etc.) it can be a nightmare for the guitar tech.

There's a lot more, but I would go on for ages (if I haven't already).

Not all festivals are such a downer, but the good ones really are the exception.

I just don't find festivals to be very enjoyable on the tech end of it. That's all.