My understanding also is that it is an anology to icecream, as in the Baskin Robin's 33 (or whatever) flavours to pick from. To me, D/s is just one of the many flavours out there, and does not claim to be superior to others, nor is it implied that vanilla is inferior. I think it is a cute term and, like all other words adopted, it just allows us to communicate with just one word to convey a situation, rather than needing a whole sentence.