Not all cultures use base 10. Some cultures are base 12 and count by the three joints on every finger (12 on each hand).

But in general, especially the western world counts in base 10 probably because of ten fingers. Peoples that didn’t use base 10 most likely had to adapt to Europeans or other cultures who did use it, and it just stuck.

There are still tons of things not using base 12 today:

Clocks are base 12 for hours and base 60 for minutes and seconds.

A dozen (eggs) is 12.

A score (years) is 20.

12 inches equals a foot, and 3 feet equals one yard.

Computers are coded in binary.

The great thing about mathematics is the fact that it doesn’t matter what base system you use, cause it’s all convertible. Digits, numbers… none of it matters as long as a mathematician knows the countable value.