When I am in a hotel, I'm really not interested in the clothing of people I don't know. Of course I can see them, but I am hardly forced to sit looking at them, even if they are on the next table. I am focussed on my own food, the company I am with, thinking about the day I am going to have, not gawking at others in the dining room.
It's not hard to pay little attention to people quietly getting on with their breakfast when you have your own interests to be getting on with.
If they were stark, bollocks naked, I might look twice. But it's not going to put me off my breakfast unless they've dunked their unmentionables in the bacon.
I have better manners than to sit staring at people, regardless of what they have on. I'm not embarrassed by what other people do, it's a pointless emotion to attached to another person. It is their embarrassment to have, or not as the case may be.
I don't get these people who can't just get on and shop/eat breakfast/whatever whilst somebody else does the same in different attire. It's a public space. Other people exist in it. Clothes don't stop people being sweaty and smelly.
If I was this bothered I would have breakfast in my room and shop online.