Re: What about regular showers?
I still don't believe the sonic mode serves any particular "spaceship" function - it's just a better type of shower overall, one that everybody in the future likes to use, save for a few oddballs. Much like water closet has totally taken over from the other sort all across the western world (and Star Trek never deals with any other sort of world), but we still add the dubya to the abbreviation.
Indeed I see like the shower vs. bath.. Some people no matter what will only take a bath. While other people will only do showers.. I'm sure it's the same Sonic vs. Water showers.
How many lights do YOU see?