Answer
Binary system has 2-digit symbols. It has least symbols than in any base digit symbols.
For example,
Person A has 2 types of currency coins, of value 0.5 and 1. Person B has type of currency note of value 10. Person C has type of currency note of value 50.
To make up value of 100, person C requires just 2 currency notes, person B requires 10 currency notes, and person A requires several coins of each type, since he has only two types of coins (symbols) to make up a value.
