I wouldn't go out of my way to intentionally leave it out. But I wouldn't worry too much if the law school purpose doesn't flow well with the personal statement either. The PS is a subjective piece, being read by a random person with their own subjective interpretation. That said, a good PS, like a good song or good recipe, will be good.
I always hated the question "So why do you want to be a lawyer?" I'm in the summer between 2L and 3L and only recently found the answer. It's because I want to play life at the big table.