It's surprising to me that more drug users aren't aware of the affects of capsaicin on the body. Your body thinks it's on fire so it releases endorphin's to protect you. Tolerance builds rapidly to this drug and so does the ability of a pepper to burn a person. When your tolerance is high enough, the heat no longer affects you. So when people dont see what the point is in eating food that is so hot you cant even taste the food, it's relative to tolerance. As tolerance builds, the release of endorphin's is no longer sufficient. So what was once a spicy pepper, may be milder. So we need more to 'get high'. At this point the flavor of the pepper or dish begins to dominate and no longer overpowers the dish. So it's not actually a hot dish anymore. Hot peppers are also rife with nutrients and with intake can reduce your risk of cancer, heartburn (ironically) and other good things.
I've been addicted to capsaicin my whole life. I'm not dependent or anything but nearly every meal has to have some level of heat to it. It's very difficult to find a perpared dish that meets my heat standrads. I have to carry around hot sauce or chile powder if I go out. As the years go by I need more and more heat to satisfy me. For example: I used to eat Jalapenos like candy but they are no longer hot to me, though they have a great flavor. The first time I ate a raw ghost pepper, habaneros were already my mild. The endorphin rush lasted for 45 minutes as I was hunched over a sink drooling out of mouth and nose. Shitting didn't hurt, pissing did though. The next superhot I ate was a Trinidad scorpion. At that point I'd already been consuming lots of really hot sauce. The heat was quite intense, but not as bad as the ghost pepper, despite being several thousand scoville units higher. The next ghost pepper affected me like jalapeno used to. The next scorpion felt like a habanero. So you see that it takes repeated exposure to build a tolerance to a certain point, like other drugs that have similar effects. I guess it's just whether or not you want to subject yourself to that intensity. I like it

. At some point I want to eat the hottest pepper known, the Carolina reaper. I know that at some point I will hit a wall and the heat wont have much effect but that is just fine.
If you want to climb the heat ladder, be cautious. Some people can get away with eating things way out or their comfort zone but it can be dangerous. If your body cant handle it you may black out, have hallucinations, cardiac arrest, seizures, stroke, or death. So start small and work up to it.