The bold is what really gets me. I've never worked in a seat-yourself restaurant, and have never really encountered the situation you described when dining out myself, except for when I had coffee at Cafe du Monde in New Orleans. Still, we waited to the side of the table while the employee cleaned it for us.
I guess because I've been in the industry my whole life, I'm conscious of the fact that it's pretty rude (someone has to clean around
you now), the staff is less likely to notice that you're a new client (you know, with no menus and half full water glasses), but mostly because you never now if the people before you sneezed/coughed/spit/threw up/bled all over the table you are now sitting at. It's just gross. People are gross.