As dumb as people that can't fill air may be, they are not as dumb as the guy that thinks he can spend a few moments showing someone, and then issue them a card to say they are qualified.
Qualified by who? - some guy with a laminating machine? No. You could even go to jail for issuing those cards, and if not, it would be a mighty fine.
This is an area where paintball skates on thin ice. Decanting high-pressure gasses is no joke. U18's definitely should not be filling their own tanks, and nor should anyone else unless they have been certified.
We all do, sure, but the guy that gets into the real trouble will be the guy that tries to do something about it -out of a desire to help others - but doesn't do all his homework.