Because it lets your math code look more like math and less like code.

    v := Vector{}
    v2 := Vector{}

to add the two vectors, currently you have to do something like

    result := v.Add(v2)

rather than the nicer

    result := v + v2

In the small scale, it doesn't seem like a big deal. In a large and complicated scientific program, it can make the code a lot harder to read.

Note: I think it is good that Go does not have operator overloading, though I think it's a shame that means it's not as good for scientific & math programming.