For me it is the fact that our blood contains iron. I earlier used to believe the word stood for some ‘organic element’ since I couldn’t accept we had metal flowing through our supposed carbon-based bodies, till I realized that is where the taste and smell of blood comes from.
This seems like a logistical nightmare for all systems related to pregnancy and childcare if it were to actually become a popular thing, like damn, just pay people for having kids its not that hard