As a yacht broker I go on hundreds of boats each year and take my shoes off almost every time and ask clients to take their shoes off also.
At a boat show if you do not want to take your shoes off you should carry your own paper booties. If you did not want to take your shoes off, then I would not think that you would want to buy the boat, and boats are in shows to be sold.
I'm not at all sure I agree with your thought process on that one.
It's similar to judging a potential buyer by their clothing or age.
And while I generally do the same thing unless otherwise advised, I do so as a courtesy. Many of the boats I've been on at shows, both in and out of water, have had carpet or other material down to protect any easily marred surfaces. The rest were pretty durable.
Just my buck thirty on it.