Programming is maybe (?) the only professional career at which members are doing passable work before the age of 10. So, it's often fated.
Lots of the manual trades - isn't their a huge uproar about child labor in textile & small goods factories? Probably not what you had in mind, though.
Passable work, for a mathematician, still means proving something original and nontrivial, whereas passable work for a programmer just means creating something that works.
Do you know a ten year old hacker?
How many out there have been programming since they were kids?