Picture a dark room full of people where you’re supposed to sit quietly otherwise they’re mad at you. Now imagine taking a wrecking ball of a child into that room. It’s your responsibility to keep them sitting quietly. And failing that, to keep them from bothering everyone else.
You don’t want drug addicts being solely responsible for a newborn baby do you? The only way to be sure that doesn’t happen is to test people.
I don’t know if the original intention was just that naïve or if it was always sinister, but it’s definitely used in discriminatory ways and does more harm than good.