Because a Computer is an Electronic Device and its main component is called a "transistor". There are capacitors and resistors and diodes and transformers etc., but the transistor is what makes small computers possible.
A transistor basically either allows current to flow or doesn't depending on what input it receives at its base. More simply, the transistor is either ON (1) or OFF (0). Since there are only two states, a base-two or binary number system makes the most sense.
Also, the RAM, which runs on latch circuits (and/or J-K flip-flops), can also have only current (1) or no current (0) at each address (or area of memory).
So, if the value of a variable (area in memory that contains a value) is equal to 6, this can be represented by the state of 3 transistors. The first is on (1), the second is on (1), and the third is off (0). As a number this would appear: - 110
It would be wrong to say the computer only reads the electronic signal. They are only ON or OFF. We transforming is to “1” for “ON” and “0” for “OFF” for our Convenient.
So it’s purely a matter of convenience.
