Why is number of bits always(?) a power of two?

Question

We have 8-bit, 16-bit, 32-bit and 64-bit hardware architectures and operating systems. But not, say, 42-bit or 69-bit ones.

Why? Is it something fundamental that makes 2

Answer 1

Byte is related to encoding of characters mostly of the western world hence 8 bit. Word is not related to encoding it related to width of address hence it is varied from 4 to 80 etc etc