Re: Garbage Collection
The number of variables can be determined at compile time. The number of values cannot. It's references that are one of the mechanisms for achieving this.
The value "5" is a different kettle of fish. Integers are fixed in size and usually take up the same amount of space as a reference. So most languages store these directly on the stack, rather than using a reference to the heap. You are wrong if you think that there is only one value 5 in a program; there could be any number and the compiler cannot determine how many 5s there are at compile time.
It can determine how many literal 5s there are, or expressions that always evaluate to 5 (i.e. constant folding). Again, there would still be multiple copies of "5" in the program, because there is no point interning an integer. Unlike, say, a string which might very well use an interned reference.
Of course, there are circumstances when it makes sense for "5" as a value to be referenced rather than stored directly, which is when you want to add some extra behaviour to it. Atomicity, is one example. Another is when 5 is not an bounded and fixed-size integer but a number you want to be grow to any arbitrary size or precision.
As for your last comment: c.f. previous argument about civility. It is a shame that you lack it.