Obviously you have never had to wear one for long periods of time. I have, and it sucks, put one on, and try to go for a 5km run, and keep the same pace. You almost have to relearn how to breathe, to keep the body supplied with oxygen. Now to keep it from fogging up, or for you not to sweat like a pig, or the straps not to dig in a little.
So what makes you want to play with a gasmask???