Any effort you put into solving it can do one of two things: prove you are human, or help label data. It can't do both. The only way to have it do both is to

Any effort you put into solving it can do one of two things: prove you are human, or help label data. It can't do both. The only way to have it do both is to make you put twice the effort into it. If you are thinking one comes as a byproduct of the other, though, you haven't really thought it through.