One doesn't just start doing heroin. Heroin is at the end of a long process of addiction, dependence and tolerance.
It often starts with pills, like Norco, either in a party setting (Norcos mixed with wine will make you drunker and higher) or because you got injured and were prescribed painkillers. Narcotics are highly addictive, so eventually tolerance builds an you start eating Vicodins. Why? Because the feeling of being high on a bunch of Vicodins is like swimming and floating on a cloud made of love and warm hugs from people you love. But soon you move to percocets because 6 or 10 vicodins aren't enough.
Eventually, you start hurting because of all the Tylenol they put in the Percocets. So then you hear from a friend about cold water extraction, You start purifying your Percs so you can get high and not feel like shyt the next day. Then you start re-capsuling your powdered Percs because they taste like bitter ass. But you realize, wait a minute, if it's in powder form - you can snort it! Soon you realize crushing, filtering and snorting Percs is both really expensive and difficult. So your dealers says, hey, wait if you want, I can just sell you powdered heroin and it will get you that super warm and wonderful feeling you love without all that work, plus it is cheaper! So you start snorting heroin.
This works for a while, maybe even a long while. But the fact is, now you're a junkie. You look forward to the high more than anything else in your life. You ignore your kids, your job, your wife, all your hobbies have been long forgotten. The cycle of addiction however is far from over, and in all honesty snorting heroin is disgusting. Snorting things causes the residue to drip down the back of your throat. Unlike Cocaine, which gives a numb kind of cooling drip that is actually very pleasant, heroin gives you a slimy, earthy, woody, nasty altogether filthy type of post nasal drip. It's quite foul actually. But when you pair it with the fact that your mind begins to envision that you're wasting the drug by letting it slowly and snottily drip down the back of your throat it becomes something you dread.
If only there was a way to simply put it directly into your bloodstream. If only you didn't have to taste it, or snort it, or deal with it. Just warm it up a little and put it in an insulin needle and push it straight in. So you do it. Maybe you get some help from a friend, then get some needles from the pharmacy, you know that you aren't gonna share them, they are yours. fukk everyone else. Why didn't you do this earlier? Jesus, this is the easiest, cleanest way for you get your fix, and you can get even more fukked up and buy less junk! Maybe even save some money! fukk, this is genius! So you start shooting up. Your tolerance builds, and honestly, man, the warm hugs of love are back. This is that feeling you miss and haven't had in years, for you do not get hugs from your wife or kids anymore, but you do get your hugs from the nod...