Interesting you’d pose the question ‘If you don’t, why?’.
If you DO, something has driven you to do that. If you don’t, nothing has.
So my answer is, because why would I? I’d guess most people don’t but from the framing of your question, I guess you do? So can I ask, why you shave your asshole? Not that I care but you started this. And if you don’t shave your asshole, why do you think people might do so? This is not a rabbit ‘hole’ I wanted to spend my evening going down.