just realized my explanation was still non-obvious. The neurotypical doesn't stress about this question. They simply click or don't and don't think about it. The autistic rule-follower wants to follow the instruction correctly.

Knowing that this is used to train cars and the result might actually kill someone kicks in my (our) strong moral imperative and makes me want to get it right even more.

I know i'm not the only autistic who gets hung up on this problem with captchas.