Darcy, I just knew someone would pop up with an exception
I'm speaking to stuff of recent vintage. There are lots of foreign motors that have all kinds of odd (to us) voltage ratings.
I believe that standard utility voltage went straight from 110/220V to 120/240V, as you say, about 70 years ago. I guess the 115V or 230V ratings came about because around then there would be both 120/240V and 110/220V installations