Indeed, the smell. Perhaps the designers are suggesting that it's sexy to share that with your partner while zie is eating hir continental breakfast. (And do we call that an incontinental breakfast? *jazz hands*)

Most of the no-wall bathroom reports were from posh hotels in Asia. If my cultural knowledge is correct (and it might not be), I think there's less taboo there about the fetishizing of toileting. But then, the Tokyo bathrooms I was in had those princess boxes that made white noise to disguise the sounds of elimination, so go figure. In any case, the people reporting on TripAdvisor had been very uncomfortable in them.