Why do we have different units for the same physical quantity?

(N/A) The value of any given physical quantity may vary over a wide range,so different units for the same physical quantity are required to express these values conveniently.
For example: The speed of a bicycle can be measured in $m/s$,the speed of a car can be measured in $km/h$,and the speed of a satellite can be measured in $km/s$.