I've been able to ride no-handed almost as long as I've been able to ride a bike.
Reckon it's partly about the bike myself.
the 24" wheeled Elswich Hopper Thubderflash (mmm) I had ages 10-15 (approx) I could do no hands on no problem whatsoever, steer round corners and all*.
Never been able to do it on any subsequent bike.
Yet when I retrieve that from the back of my parents' garage, I can do look no hands all over again.
*I was very kind to my parents. I only did it when they weren't looking. Younger guy, oon the other hand ...
(No hands on the back of a tandem trike is cheating). But fun.