It’s much the same reason why you wouldn’t go to work wearing a days old, stained shirt and ripped pants — yeah, you’re more than likely going to work just as hard and as well than if you were wearing clean clothes, but that’s not going to stop people from judging you based on your appearance.

Most academics write code to just work. Not work well, or to be generalized, or to be efficient, just work. And while that’s absolutely fine, as your results being reproducible from the code is all that really matters, a lot of people don’t see it that way and will only see code slapped together haphazardly and dismiss you because of it.