Computers don't understand decimal though. They work on binary.
Humans don't work on binary so well, but binary doesn't convert well to decimal. Starting a new "level" in hexadecimal coincides with a place value in binary. 0F to 10 is 1111 to 10000, 1F to 20 is 11111 to 100000. I guess it's harder to make typos and easier to spot them if you're typing something more easy to read than a jumble of 1s and zeros.
I'd be in favour of reinstating the old babylonian base 64 numbers. Far more elegant symmetry than our ape digit based system.