They might not be able to stop the bleeding
WHAT?! WHAT?! Have you half your brain tied behind your back to make it fair??!! What do you think they do when they’re finished sucking your blood? let you die? why would they do that? Do you think thy suspect that the person is going to be so scared of giving blood like a teenage girl doing dor yesharim that they will never give blood again? may as well kill them. that seems to be the prevailing opinion of this thread. kill popa b/c he wont give blood.
Not everyone i s so scared of dor yesharim so theres no reason to kill him, so probably they have a way to stop the bleeding. In fact I know they do b/c i give blood all the time apparently unlike Health.