>>149413339Serious answer: they use them for skin grafts and cosmetic testing. The reason secular, medical circumcision is so popular is that even though it serves no practical purpose (aside from avoiding smegma but that's complicated) is because doctors actually make a lot of money not only doing the surgeries but selling off the excess material.
Schzio answer: Witches need the flesh unbaptized babies to make flying potions. Infant foreskin allows them to do it without actually having to kill the baby. Doctors sell the foreskin to witches for fat stacks of cash.