why scientists have created the S.I units of measurement?

scientist created s.i units to defined the amount different quantities.S.I units make it easy to compare the amount or intensity of two or more quantities. 

this can be understood with a simple example :

suppose if there is a mass of 10 kg.

and if we say the mass is only 10 then we are not providing any defined amount because without units we cant define it.

10 can be anything kg, litre ,gram. anything and we know there is a big difference in 10 kg and 10 gram so without units we can never know that it is 10 kg or 10 g.