why are there no Fb, E#, B#, Cb notes?

[john]

I've just started teaching myself to read music, and have come to the conclusion the it would be a whole lot easier if "they" had included these notes to create a tone between all the notes from A - A, having semitones between the letters. I know that Fb = E# and b# = Cb. It would have made more sense.
I don't think I explained it properly.
if you play all 12 notes from A - A it goes like this:
A - A#/Bb - B - C - C#/Db - D - D#/Eb - E - F - F#/Gb - G - G#/Ab - A. Each dash represents a semi-tone. My question asks why these notes do not exist, is it because there only exists these 12 notes? Why not have the notes go A - A#/Bb - B - B#/Cb - C - C#/Db - D - D#/Eb - E - E#/Fb - F - F#/Ab - A , and do away with "G"? I know that in the end I am just going to have to accept it and learn, but for me, I'm teaching myself, which is difficult enough.