Thought Experiment time. Ladies, you're in the hospital, just having given birth. The doctors tell you that your baby has to go in back for 24 hours, to get vaccinations, be observed, etc. You cannot watch the process, you have no legal right to interfere with the process, you can only wait on the other side to take home your newborn one day later.

But you trust the hospitals, right? You trust your doctor. You trust them to give you your baby. They would never make a mistake. Only... when you look into the process, it turns out that hospitals hand back the wrong baby THIRTY PERCENT of the time.

Would you trust that you are holding your baby? Or would you get it tested?

Doesn't matter if it's malice or mistake, you'd want to be sure that's your baby. Mandatory testing takes care of that.