I've had my haircut mentioned at work… because I'd had a haircut. It's people trying to be nice or make conversation, and neither of those things are unprofessional.
I understand your point, of course, but it does not actually explain theirs.
I work from home so the only person who remarks on my hair is my wife, and her comments, if overheard, might pass for misandry. I'm trying to forment a Twitter mob against her in response.