even though powdered opium, de-odourised (that is, de-narcotinised) tincture of opium -- aka laudanum, and paregoric are still listed in the united states pharmacopoeia, it can be very hard to get because of periodic supply chain problems, ignorance of the fact that it is still available (by doctors and chemists too) and other problems. b&o products are also practically gone and pantopon disappeared long ago.
opium is a combination of more than 50 alkaloids of two main types as well as oils, gums, resins, proteins and much more, and is especially useful for gastrointestinal problems of all types. it also lacks some of the potential problems that concentrated morphine may have. It can be grown in the united states and different parts of the opium plant including the dried juice (gum opium) and has been part of home remedies for thousands of years.
its slow onset of action and long duration of action when taken orally, the effort and time it takes an end-user to make it from scratch, and self-limiting nature in terms of the bang it produces (also when taken orally) make it something which can be used as an agent to maintain or detoxify non-iatrogenic narcotic-dependent persons in the same fashion as methadone, buprenorphine, dihydroetorphine, extended-release morphine, dihydrocodeine, hydromorphone, oxymorphone and piritramide.
opium for smoking is a different product which also has a very involved preparation process which tends to irk non-medicinal users.
it can be grown by people in small plots at home just like pot.
aside from all this, marijuana and opium are apples and oranges as far as analgesia, so we need both to be in common use. it't true.