Why does we have five fingers?

Normally, most of us have 5 fingers. There are various theories that suggest the reason for this case. And some of them are,

A theory suggests that we have 5 fingers because together they make a perfect strong grip. Using them, we can operate small objects with great control and precision. 

Second theory suggests that there is a 3 molecules called Bmp, Wnt, Sox9 are responsible for our 5 fingers since embryonic stage.

Third one called, Limb law, based on the length of the fingers, this law helps us to calculate the number of fingers we should have. Limbs law using it's mathematical model comes out with a number 9.42 per hand. But, the one side of the hand is attached to the arm and other side is held loosely. Therefore, the final answer comes out to be 4.78. That's 5 fingers.