I was shooting before I was 10 but only under adult supervision
But, legally there are lots of things you can’t do without having your own shotgun certificate and firearms license, including having access to the gun safe
If you’re a farming family, it would be helpful, useful to be able to say to your teen ‘can you pop back to the house and grab a gun or some more ammo so I can shoot this rabbit/put this injured sheep out of its misery’ and that would require the teen to have their own licence
Without a licence, the teen can’t even legally know where the keys to the safe are kept, let alone open it
Equally, there isn’t much harm in a sensible team wanting to shoot 150 clays as practice before a competition without close supervision which would again require their own certificate
Or, a teen competing at clay shooting who gets a lift to competitions with another family
If the child didn’t have their own licence, the driving parent would have to complete paperwork to temporarily add the gun onto their licence for the duration of the journey there and back, then more paperwork to transfer it off their licence
All easily solved by the child having their own licence
I can think of half a dozen more scenarios where it would make sense, none of them involve a 13 year old holding up a bank or post office