Gotcha. I think the OP was specifically about being dressed formally, so that's why I was asking.

Other than smelling bad, why does it matter if I'm well groomed to passerbys or that I care about my appearance?

Again, I'm talking about potentially flight attendants, the people at the gate check, etc. we are ships passing in the night, they are there to make sure I'm me, and I'm just passing by. I agree that if you wear something that is offensive, like swear words or images that maybe considered obscene, that's not ok almost anywhere imo. But if I wear unbranded sweatpants and a hoodie, how would that make me being disrespectful? I'm not there for any person. I'm not there to win favor. They are there to do there job which is to check me in or provide a service, or as far as random passerbys, we are just sharing a space.

So do you believe that it's disrespectful to dress down or is dressing up just more respectful in your opinion?