You seem to be of the opinion that this hobby involves kids and toys and that the users are playing with them.
A lot of the people who are testing their skills are adults who take it very seriously indeed.
It can for many be more realistic than what the military do with blanks and thunder-flashes, after all the military don't actually shoot projectiles at each other.
If you look at what I wrote, I said no such thing.
Guns are in my view tools intended for a serious purpose. Their primary purpose is either target shooting, or killing things that need killing (be that animals who can feed you, or bad people who intend to do you harm). They are extremely dangerous tools, so training in disciplines such as never pointing the muzzle at something you're not willing to destroy needs to start early. Airsoft provides contrary conditioning to this crucial discipline, whether it is practiced by an adult or a child.
Studies have shown letting kids play with toy swords and guns is actually good for development. I'll try and dig out a link.
I'm aware children will often make guns out of anything to hand. Nonetheless, this is not something I encourage for the above reasons. My own preference would be to purchase something along the lines of a Ruger 10/22 or a Marlin Papoose and teach my kids how to use a
real gun from an early age. Take the mystery out of it, and drill the rules of gun safety into them at the same time.
Unfortunately the mountain of paperwork required in the UK makes this impractical so I cannot follow my preferred parenting trajectory (put unintentional). My aim for a long time has been to emigrate to the USA or Canada - where it will be much less problematic to obtain real firearms. I do not want to have to unlearn bad habits should I find myself in that situation.
But as I said earlier, this is just my opinion. If airsoft gives you pleasure, have at it. You don't require my endorsement.