The palm of the hand HAS to be the worst source of blood...right?

[Ionathus]

I feel like I see this in TV shows and movies all the time. A character needs a few drops of blood for whatever reason, so they cut themselves on the hand or on the finger. A short list that comes to mind now:

• In National Treasure, the main character cuts his thumb to spread some blood on a cylindrical "stamp" and get the next clue
• In Pirates of the Caribbean 1, giving blood to the cursed chest of gold always comes from the palm of the hand. The pirates cut Elizabeth's palm against her will, and then later, Jack and Will both willingly cut their palms for the same reason.
• In Damsel (the new Millie Bobby Brown film), two characters need to be "joined by blood", which they accomplish by cutting their palms and holding hands to let the blood mingle (gross).

(I'm certain there are others -- I feel like I see this trope A LOT -- but those are the ones that come to mind right this moment. Weirdly, Jerry Bruckheimer directed two of them. Connection...?)

Anyway, to my point: that can't be the best way to go about that, right? Hand wounds feel like the absolute worst spot just in day-to-day life, and I don't even live in a swashbuckling or adventure story. Wouldn't it make more sense to make a small cut on the back of your forearm, or your bicep, or somewhere that doesn't require a ton of manual dexterity and can be easily bandaged? Obviously you wouldn't want to, like, open a major artery since that would be a different kind of problem. But I feel like there have to be better options than "the part of my skin that I use to touch every external object".

Is there something anatomically "perfect" about the hand, where you get a reliable blood supply but there's no danger of bleeding out? Do the wounds heal more quickly or reliably? I know finger-pricks have a long tradition of consistent blood testing, so maybe there's something else going on here that I don't know about.

And of course, I understand that cutting the palm of your hand is really visually interesting to represent a token blood sacrifice. I totally get why filmmakers choose it, for the symbolic value and the "ouch" factor you get from audiences imagining cutting their own hands. But come on! There's gotta be a more practical spot to get a teaspoon of blood from!