Morse code query?

Question

Why aren't the codes . . _ _ or _ _ . . used?

There are other more complicated codes with more characters used so why did these two (and maybe others?) get left out of morse code?

Many Thanks

Answer 1

probably because they'd be easily confused with other letters. .. = I and -- = M. so a letter that is ..-- will get confused with those 2 letters.  there's also a lot of training that goes into teaching MC that helps to train the ear.