It's a cultural thing.
We have 10 fingers, and a lot of people counted that way.
There's another way where you point to a finger bone with a thumb, that way you can count to 12. They mostly lost out to 10, but you still see them all over the place. Most notably the clock. It's 12pm somewhere in the world right now.

Programmers work in powers of 2, and 16 is a convienent power that closely mirrors how we used to set up memory. There are 16 combinations of four 1s/0s in a row and 8 1s/0s in a row make up one computer byte. Hence why you see programmers use numbers like 1F A2 FF

You could count to any number, but these are some of the most common ones.