The first guy to build a classical guitar, forgot to put them on. Everybody else copied him, and like most anything else, if you say or do it often enough, it becomes true. So, today, it is still true that we don't have dots on the classical guitar.
I read that somewhere on the internet, so it MUST be true.
If I were to tell the real truth, I would have to admit that I have absolutely no clue as to why there are no fret dots on classical guitars.
Tony