Question related to memory storage capacity of data type....in C

Question

I found that "int" data type have a two different memory storage capacity like....
4 byte || 2 byte(which is depend upon type of machine architecture)
[1 byte = 8 bits]
1 bits have possible value such as "0" or "1"
"0" --> off[0 - 0.5v]
"1" --> on[some voltage between 2.5 - 5]
Here my question arise....
Why they use(create compiler && OS) which use 4 byte || 2 byte as a memory storage capacity for "int" data type
Instead of using 1byte or 3 byte as memory storage capacity for int data type....
What is the reason behind it?why they create like this?
Also also please answer me why they(OS) use
1 byte memory location for "char" data type?
Also for double, float...etc

Answer 1

Thank you NotAPythonNinja for yours clear explanation......😊

Answer 2

NotAPythonNinja can you tell why we aren't using sizeof(int) as 1byte?
and also tell why 1 byte is enough for char data type.....?
please tell me what's the reason behind it