Why is 'C' not B sharp and 'F' not E sharp.

The chromatic scale is A, A#, B, C, C#, D, D#, E, F, F#, G, G# = 12

The hypothetical scale would be A, A#, B, B#,C,C#,D,D#,E,E#,F,F# =12

I'm probably missing something, is it to do with the layout of a piano ?