I remember seeing an Oprah show on this very topic (must be 20-30 years ago). She asked the audience if they snoop into medicine cabinets, etc; also if they pull back the shower curtain to see if the bathtub is clean.

As someone who has more than once pulled the shower curtain closed to hide a bathtub I hadn't had a chance to clean before a visitor arrived, I was a bit shocked at the large number of people who admitted to such snooping (including, IF I recall correctly, Oprah herself). Until that day, it had never occurred to me that people might even THINK of snooping, let alone DO it...