It must be that way in order for the number system to be consistent. If you look at the pattern of numbers raised to different powers, going down to the power of zero, you will see. Example (each time you divide by 10, so you will get 1 when you divided 10 by 10)
10 to 5th power = 100000 (10x10x10x10x10)
10 to 4th power = 10000
10 to 3rd power = 1000
10 to 2nd power= 100
10 to 1st power = 10
10 to zero power = 1
likewise
10 to -1 power = 0.1

It works for any number
5 to 3rd power = 125
5 to 2nd power = 25 (125 divided by 5)
5 to 1st power = 5 (25 divided by 5)
5 to zero power = 1 (5 divided by 5)