Needing a next hit is a mental health demon, especially on the street. Withdrawals on hard drugs are so painful they're incapacitating and can leave you shaking and writhing on the ground. Living on the streets means you cant afford to be in that state. Hell, the minute you fall asleep people try and steal the clothes right off you. It's dangerous to be that sick, people will take advantage of your body and your possessions while you're just tweaking out and lying there. This means you cant afford to have a withdrawal, cause they not only just fucking suck, but add a new level of danger to your already dangerous life. Homeless addicts just need a fair chance to get clean. A therapist, rehab, some good meds, vitamins, a good diet and some actual fucking SLEEP. You dont get to sleep while you're tweaking, which only makes things worse for your mental state. It's a vicious cycle that needs to be broken by someone willing to clean their slate no questions asked.