Oh does insulin have a thick rubber stopper? I'm a lemmy stereotype and so my only experience with injections is estrogen

Aye, and besides drug users on the streets, that's who the top picture was actually for. I can't recall how many of those signs I've seen when I was picking up needles with my insulin. I also know my uncle reused his up to 10 times or so. Worst I've ever gone was like 5-6. It's actually quite difficult to get needles when you're not at home and forget some (and they're annoyingly easy to forget).

Those were made up harder steel which can't be sharpened to the degree softer steel can be. Harder steel shatters if sharpened since harder it is brittle it becomes.

So reusable needle are blunt, so injections are painful. And as mentioned by @Natanox@discuss.tchncs.de they used to shatter inside the body after a few cycles of autoclaving.