Basically it's because 12 is more divisible than 10. Factors of 10 are 1,2,5 and 10. 12 has 1,2,3,4,6 and 12. This gives more flexibility when discussing numbers. Our time is technically using base 12, which is why we can say quarter past 4 and it means a traditional whole number. That's the argument I've heard anyway
Basically it's because 12 is more divisible than 10. Factors of 10 are 1,2,5 and 10. 12 has 1,2,3,4,6 and 12. This gives more flexibility when discussing numbers. Our time is technically using base 12, which is why we can say quarter past 4 and it means a traditional whole number. That's the argument I've heard anyway