WHY DOES 0! =1 ?

Many of us are confused why 0! =1. This is the best explanation that I have came across.

If you have 3 playing cards in your hand, you can arrange them in 3! different ways. In other words you can put them in 3 x 2 x 1 = 6 different orders.
If you have 2 cards, you can put them in 2! different ways which is 2.
If you just have 1 card you can only arrange it 1! ways which is 1.
But if you have ZERO cards then there's also one way of doing that!