It seems to me that because these guns are mainly marketed as a "toy" due to the fact that all the cheap readily available "airsoft" guns the public sees are the clear plastic ones from Canadian Tire and Wal-Mart that even though those stores do have a policy, on paper at least, of only selling to those 18 and over, most would come to mind that since its a clear plastic gun that it's okay to hand them over to ten to fifteen year olds.
Most people are even further pampered by the fact that they don't do their own research into the world of airsoft and just blindly believe whatever the news medias say about airsoft, when if they did even ten minutes of research on a website with some good information on the sport they would find that most players treat and handle their airsoft guns as if they are their real world counterparts.
I think because paintball guns don't remotely look like any "real-steel" gun and most PB guns sell starting around $150~300 at most places including Canadian Tire and Wal-Mart and the fact that there seems to be a bigger PB community, to most people's eyes at least, that PB is to be played by the young adult crowd at least sixteen or over, or at least for most places where people play they have that age rule, where strict rules are enforced to ensure the safety of everyone, unlike airsoft... which seems to be a rouge game where people just play in their backyard... which couldn't be further from the truth.
Since the very nature of airsoft is to have the guns look, feel and function as their "real-steel" counterparts, most misinformed people who have seen a "real" airsoft gun, and not the clear plastic ones, have the conception that airsoft guns are dangerous. With proper handling and use, airsoft guns are no more dangerous than PB guns. Yes if you get hit by a plastic BB, depending one where you get hit, it will hurt.. but so does getting hit by a PB...
Granted I may be mistaken in something in everything I just said, since I've never been to an actual game yet, from that's the conception I see people have about airsoft from my own research into the sport. Feel free to correct anything I just said.