why didn't Jackie Chan voice Jackie Chan

Too busy making movies.

I have an unbelievably long ignore list.

I've always wondered that myself is call Jackie Chan Adventures and is not Jackie Chan doing it.

Wait, he DOESN'T voice himself?

I've read that Jackie Chan was originally going to provide the voice of his character himself, but he had never worked in animation before and found voice acting to be too difficult. So he told the producers to find somebody else who sounded like him and he would just do the live-action segments instead.

Because His english wasn't that good back then, even he admits himself in interviews as well. Voice acting takes alot of quick pacing and talent to do, so I think the guy who did the voice of Jackie (James Sie), was not only grasp a younger sounding of Chan but also delivers hilarious dialogues.