Even if it's not, your default hostname when using a MacBook Pro is typically "<username>s-MacBook-Pro.local" which reveals you're using a MacBook Pro. That info leak probably doesn't matter, but generally you want to reveal as little information as possible.
What kind of person cares enough about anonymity to change the comment in their ssh key, but not change the default hostname of their Mac? That person is very inconsistent.
Because it helps usability when the user is editing ~/.ssh/authorized_keys - if the default is not changed, the key comment has some context, so finding the right key is easier.
I strip comments from my SSH keys too for the same reason you do. But most people don't seem to care and there is a reason for the default.
