Comment by graemep

A number of hotels that were built with this lack of privacy (including one I love - but its been fixed there though - more subtle worse as you could see in from the stairs) were all designed by the same architect who is said to have had a kink about looking into toilets.

Maybe he started it, and as his hotels are (otherwise) lovely it made it part of a cool aesthetic and was therefore copied?

https://en.wikipedia.org/wiki/Geoffrey_Bawa