Competitions are simply about determining who does any given thing best. If not so much as a single note is played in air guitar, why would an air guitar competition require competitors to play notes? The question seems silly.
Like Lt. Facemelter said, though, these are as much performance art as competition, so it doesn't really matter. No one is forced to attend these shows. Air guitar is not taking money out of the pockets of musicians (in fact, many air guitarists play there guitar or other instruments in real bands). It's just good, clean fun. Maybe not clean. But fun. That's why these shows regularly sell out.
You're not the first air guitar skeptic. I've heard from plenty of folks who were dragged to their first air guitar show expecting to have a bad time, only to be converted and return year after year. Videos don't do it justice.
Besides...people have been playing air guitar for decades. Taking it to the stage was a natural progression. I don't know of anyone who air cooks, but if it catches on, I'm sure that'll become a competition, too.
Come check out a show. I guarantee you'll have a great time!
I hear this all the time from "real" musicians -- "what's the point?" The point can be summed up in one word: "airness." It's when the performance transcends just playing along with your song, into an art forma all its own. It's a difficult concept for many to grasp, but for those of us who compete, it's performance art...and insanely fun.
I've "played" the Key Club, the Roxy, and the Troubadour in LA; and I'm getting ready to "Rock The Casbah" in SD, and Busby's East in LA next month. Not many average Joes can make that claim. You really should come see what it's all about.
"To air is human, to air guitar is divine." -- Bjorn Turoque
Rule your air.