We've seen this and the changeling samples in DS9 without someone beeing 'tortured' with barbaric needles. How does it work? Is it like a hypospray? Obviously nobody feels it when his blood is drawn that way. Rom took a blood sample with sleeping Nog just to see if he's a changeling or not.
And yet, in "The Deadly Years," Chekov complains about McCoy using "needles" to take blood samples. So I gather it was less painless in the 23rd century? (I rewatched the ep the other night and we never actually see the blood being taken, just Chekov griping about it afterwards.)
In any case, it probably involves making holes, as McCoy thinks drawing blood without leaving holes should be impossible in "Obsession"... Might be the standard hypospray (which is used for the bloodsucking in, say, "The Adversary") simply delivers a numbing agent that it subsequently also withdraws, taking lessons from the common gnat. Might be the hole in question is made using special future techniques that close it afterwards (after all, dermal regeneration is an art form well mastered in Star Trek). Might also be 24th century devices use the transporter effect and would make McCoy gasp like he did in "Obsession". Timo Saloniemi
When we actually reach the 24th century, I doubt any blood extraction of any kind will be required. They'll look back on it as vampiric. A simple scan will probably suffice.
I think there will always be a need for blood samples. Sure, a tricorder scan can probably easily determine someone's blood type and whatever, but when trying to determine a cure for a disease even the best computer simulation probably can't beat actual experimentation with the real thing, IMO. Or it could even be a case that real blood samples might be considered more trustworthy for security reasons maybe.
My mental version of the hypo contains many tiny "smart needles" that snake their way through fabric to enter the skin through multiple microscopic entry points.
Explainable by many things: McCoy jabbing him as opposed to pressing it gently, Kirk's over-sensitivity to pain as another side effect of the vaccine he was allergic to, Kirk being annoyed that McCoy interrupted his urgent message for Pike. Spoiler: Fanfiction spoiler I once included a scene in a fanfic in which Kelvinverse McCoy enlists Sulu to help him pressure test a bunch of hypos by pressing them against a test pad. (Chapter 25 of "Contemplative Silence", "Acceot No Substitutes", if you're interested.) In case tech fails, returning to less advanced tried and true methods can at least tell you something about the problem. Plus having actual samples allows you to experiment in the real world. A simulation based on scan results can't predict every possibility.
That may be where the actual needles came in. Taking marrow samples requires access to the middle of bones. Hyposprays seem like they don't have that kind of range, let alone the ability to pass through the outer, hard part.
The hypospray seems to be an advancement on the idea of the jet injector https://en.wikipedia.org/wiki/Jet_injector
So does drawing blood still hurt and people suppress the pain? https://vignette.wikia.nocookie.net...dth-down/350?cb=20160710202152&path-prefix=en
Vulcans feel the pain and pretend they didn't. Klingons claim the pain is far more intense than it actually is, just so they seem braver. And the women of Sigma Draconis VI say "Pain! Pain! What is Pain?"
Maybe the blood draw devices have a kind of tiny transporter that just beams the blood into the tube? Wait, that can't be it, given we see the tube fill up. Maybe it makes a micro-wormhole inside of your vein, so you just "bleed" directly into the closed container, with no needle involved?
"I'm sorry captain, anaesthetics just don't work in the vicinity of warp nacelles, everybody knows that! <nasty grin>"