They are always free to choose another drug and walk away from this company. The market is free like that, the invisible hand distributing only where demand exists.
And yea, the pharmaceutical companies are to blame -- of course it's not all their fault, but a huge, HUGE % of it is. It started with over-prescribing of pain pills. Particularly OxyContin. The pharmaceutical companies and their reps, intentionally and knowingly, told the doctors "don't prescribe a higher doseage, prescribe more pills of the lower dose" -- along with giving them financial incentives including straight cash kickbacks. They knew how addictive these drugs were, and they didn't care, if any of them say different they are flat out lying.
Then the government steps in, the DEA either pressures the doctors who are over-prescribing until they give up and quit, or they shut them down directly. Now there's a vacuum with a ton of cold hard cash floating around in it - the addicts still have to have their opiates but the suppliers (which were their doctors) are gone... what an opportune time for the heroin dealer to step in and fill the void?!?! And that is exactly what happened, and is happening right now everywhere in the country.
And it's not like the DEA doesn't know this is what happens, they would have to be bumbling idiots not to, but they have to show results in order to justify their budgets and keep their jobs.
See my other comment, but it appears that there are a small number of doctors "robosigning" prescriptions, almost certainly in the knowledge that the drugs will be resold into the black market.