[cogman10]

This is basically the reason.

Another part of it is the fact that it's a lot easier to represent stuff with hex if the bytes line up.

I can represent "255" with "0xFF" which fits nice and neat in 1 byte. However, now if a byte is 10bits that hex no longer really works. You have 1024 values to represent. The max value would be 0x3FF which just looks funky.

Coming up with an alphanumeric system to represent 2^10 cleanly just ends up weird and unintuitive.

[Spivak]

We probably wouldn't have chosen hex in a theoretical world where bytes were 10 bits, right? It would probably be two groups of 5 like 02:21 == 85 (like an ip address) or five groups of two 0x01111 == 85. It just has to be one of its divisors.

[shultays]

  02:21

or instead of digits from 0 to F, the letters would go up V. 85 would be 0x2k I think (2 * 32 + 21)