I agree just killing for the sake of killing, well that's not good.
but we can't put a face on the situation as if we're forcing a loving happy cow family to have extra kids and then stealing the children from them to slaughter them. everything is artificially insemination now (on big farms)
I don't know for certain, but I'd bet that more cows are needed for meat production than for leather, so reducing demand for leather wouldn't reduce demand for cattle. (this is just my therory, assuming the same cows are used for meat and leather, which may be incorrect . any FFA members out there??)