Exactly. It was 3 years before I would let my son hunt deer. My standard is all shots in 4" at 50yds. It took me 3 years to figure out that he couldn't focus on normal open sights past 25yds and needed an aperture. ( my kids don't get optics yet) Remember there is more to hunting than taking a gun in the woods. You have to be able to humanely harvest Gods creatures we owe them that.As said before, it depends on the kids' maturity and mental capacity ( this goes for the parent as well ), which age he/she is ready to be a gun user. I was in the woods by myself with my own single shot gun at the age of 7 or 8. I grew up around hunting and guns and I was taught deep respect for them early. Some kids don't ever need to be near guns, and some kids need some serious training.
I would never push or impose a gun on any kid. Let the kid prove he/she is serious about it and let them prove the interest is there. Otherwise the Parent is basically making the kid do something they are not old enough for. Sort of like the dad who wants his kid to be a sports star when the kid prefers ballet.
If the kid has the interest, expressed interest, then do it. The younger the better. The younger they are the more they learn and the more they remember for life.
I didn't get serious about guns and hunting with my nephew until he about 10 years old. He got to the point of constantly bringing it up and hounding me about shooting and hunting. I knew at that point... he is now ready.
Just because he jumps up one day and says, "I wanna go hunting" does not mean run right out and buy the kid a gun and take him hunting.