The short answer to why we use it is that we inherited it - base 12 of hours/months from the Egyptians and base 60 of second and minutes from Mesopotamians (who got it from the Sumerians).
Egyptians used base 12 a lot for a similar reason that we use base 10 a lot. We use 10 because we have ten fingers, and they used 12 because one hand has 12 knuckles (they'd count on one hand). But it was handy because there are 12 lunar cycles, so it helped keep things more consistent.
Base 60 is also handy because 60 is first number divisible by the first six counting numbers and by 10, 12, 15, 20 and 30. If you use 60, you have options! Note that we also use 60 for angles and dividing up the globe.
Yep. Your four fingers have three knuckles each. You count along them with your thumb. Then each count of 12 is counted with an extended finger on your other hand. Extend all five fingers and you have 60.
I accidentally came upon this same system messing around during long periods of boredom, and now I do all my counting this way. I also include the base joint of each finger so I can count 4 per digit
Yes, 60 is pretty much a goldilocks number that is small enough to be easily graspable for most humans, but still a highly composite number (11 factors!) so it is neatly divisible into many smaller units.