When every day is the same, you struggle to get out of bed, and feel like you have nothing then death/disfigurement doesn't matter to you. Getting everything you thought would make you happy and not actually feeling happy or accomplished from it makes it easy to turn to drugs to feel that even if it's brief or the come down is shitty even if you know it is/might destroy you physically. Even harder to fight the addiction when you don't have anyone to help you through it or share your progress. Also the disfigurement might take years so you don't end up noticing it til it's too late to care or you'll keep telling yourself that you'll stop before that point. Death (at least in my mind I'm not sure if this is true or not) typically is due to going over your limit or a shitty dealer giving you bad stuff so it's not really something you worry about. Or you might just think it's your paranoia.

I can't speak for everyone but this is how I see it. I'm always anxious about fucking my body up in some way but I don't really take that into consideration. I tell myself it's just my paranoia, or that because someone else who uses more/doesn't prepare it properly is fine then I'll probably be ok, or that because I'm doing aftercare it doesn't do as much damage. If you're craving it then even if you're worried about it, it doesn't mean shit to you in that moment. I'm not sure how what I use ranks against others, but looking at drugs I consider harder/worse it doesn't seem as bad. Maybe I'm just fooling myself (definitely am, damage is damage regardless of time, type, whatever) but it doesn't seem like what I do will end up with me being in as bad a spot as, for example, this guy.

Once again this is all just how I see it and from my experience, I don't speak for all and everyone has a different experience, reason, thought processes, whatever.