Not that old, but my gosh, I still try to dress with some decorum when I travel. I’m sorry, but if you board a plane in shorts and some ratty t-shirt perhaps you should have checked out Greyhound, or whatever other bus line is still available.
IMO, you can dress comfortably, but you can also maintain some dignity. Also, perhaps dressing up a bit raises the morale of those around you.
And by the way, germs have been with us since Adam left the Garden. Lighten up.
When I watch reruns of Perry Mason, I always smile when I see people getting off the bus in suits or a woman in a necklace. I also smile when stranger knocks on a door and the lady answering invites them in....