Young/Kid Goku from Dragon Ball (original series) was voiced by a woman.
Bart Simpson was voiced by a woman.
Bobby Hill from King of the Hill was voiced by a woman.
Could it be because there are a lack of good young male voice actors (in their early teens or younger) to voice child-age male animated characters that the creators of many shows have no choice but to hire actresses who could do teenage boy or little boy voices?
Most Helpful Girl
Most Helpful Guy
Because women can imitate child voices very easily compared to men.
And it's cheaper than having to constantly hire child actors every time they reach puberty.