I used IV drugs for a very long time, and managed to destroy a lot of my veins: they were not great to begin with and nothing like Bluelight existed back when I started using - I didn't take very good care of my veins because I didn't really know there were ways to do so at that time, the only real advice I got back then was not to share needles. Plus it was harder to access HR supplies like clean syringes (so I reused my own needles, a terrible idea as they dull extremely fast) and I was a desperate heroin addict so was more worried about getting drugs into me ASAP than the long-term consequences. Much of my IV practices/technique came from trial and error. It got to a point where I could hardly find anywhere that would register blood, it would take me hours and I would be in tears.
And I still NEVER injected into my groin. I knew enough to realize that the groin and neck were NOT wise IV locations. I found alternative locations on places like the insides of my legs. I even injected in some unusual places like the lower abdomen, which I wouldn't really recommend but is still safer than the groin. But places like the legs and the upper arms lasted me for a pretty long time because by that point I had become more educated/experienced about how to find veins, (such as feeling for those that are not visible or determining locations based on following the vein up from a previous injection site) and had more access to fresh needles, etc. I think what mainly killed the rest of my veins was injecting dope with a high level of acidic impurities without proper micron filtration.
I am now good at educating others on things to do and to avoid, and most people who say they have no other alternatives than the groin or the neck are mistaken in my experience. They just don't yet know where those alternative locations are or how to hit them. It can be learned
And getting to the point where a lot of your easily usable veins are damaged is preventable! But if you've already done so, there
are ways to at least prevent further damage and find new injection sites that are safer than the groin. OR, someone could take a think about how maybe it's a sign that it's time to quit
EDIT: I know this doesn't really answer your question, but I thought it might still be useful to you or someone else who happens to read this. I do know of a couple people who injected into the groin or neck when their other veins weren't collapsed and can tell you what they said if you want. (For example one reason some people inject into the groin as opposed to, say, the arms, is to hide the needle marks - but to anyone reading, in the interest of HR, there are better ways to do so).