Salem has it's own set of rules for everything.......lol.
I am thinking that years ago, perhaps, this blood & DNA testing was not done, but it seems in this day and age, with kidnappings, runaways, etc. that perhaps it is a safeguard to positively identify someone as the person/baby who was taken, etc. Just read of a little baby girl, taken when 8 hours old, in Florida, who was found living in North Carolina, having been lovingly raised by her mother, the person who had stolen her. Seems the "mother", was living in Fl., suffered a miscarriage, and within a few hours, donned a nurse's smock, took the baby for "tests" as she pretended to be a nurse.
My children were all born in Illinois, and while they had footprints done, they also had blood tests, but only because of the RH factor...(I am negative) to make sure their blood was o.k. But times change. After all, back when Days began, no cell phones, smart phones, computers, or 6" spike heels. LOLOL