Mutation Testing - Reason

Mutation Testing, has a lot of false positives. Despite those false positives, why and when should I use mutation testing?

For eg.

public int add(int a,int b){ 
return a+b; 
}

public void testAdd() {
add(2,2);
...
}

if the mutation results in, return a*b

the test case would still pass, but it should not.