Why swap doesn't use Xor operation in C++

I've learned that Xor operation can be used to implement effective swap function

You learned wrong, I'm afraid. XOR swap is outdated: if it was ever reliably faster than using a temporary value then it shouldn't be on modern compilers and processors (where by "modern" I mean roughly the last 20 years or more). You say it was faster for you, possibly you should show your benchmark code and see whether others get the same results.

Aside from the fact that your code only works at all on integer types, it has a fundamental bug. Try this with your version of swap:

int a = 1;
swap(a,a);
std::cout << a << '\n';

And the effectiveness depends on where you use it.

On a normal cpu, the normal swap for two integer variable looks like

$1 <- a
$2 <- b
a <- $2
b <- $1

4 ops, 2 loads, 2 stores, and longest dependency is 2

In the xor way:

$1 <- a
$2 <- b
$3 <- $1 ^ $2
$4 <- $3 ^ $2
$5 <- $3 ^ $4
a <- $5
b <- $4

7 ops, 2 loads, 2 stores, 3 logics, and longest dependency is 4

So at least normally swap with xor is slower even when applicable.

I think the most obvious reason is that the XOR operator only makes sense for integral types.