That's weird, right? I mean, if you need blood for a Klingon oath or a magic ritual, cut yourself (or your friend, or your Sith apprentice) somewhere that's not going to hurt for days and limit the mobility of their hands, somewhere that's easy to bandage to limit the chance of getting infected.

I mean seriously, they always cut the hand instead of scoring, say... the top of the wrist or something. Maybe bloody their nose? That heals pretty quickly. Or if you need a lot of blood, head wounds really gush. Maybe behind the ear?

Just stop, Hollywood.