c and s can also make the same sound. c is incapable of being unique, by itself it only mimics other consonants and is therefore redundant.
x is just ks together.
Some other languages have also made w and y redundant--certain vowel sounds pronounced in quick succession just naturally create that sound, e.g. "ee" and "ehh" sounds make a "yeh" sound when said together, "oo" and "ah" naturally make a "wah" when said together.