This would make sense, except methadone clinics, the only places authorized in the US to prescribe methadone for opiod addiction, are not free.
There are both public and private methadone clinics. Public clinics are cheaper, overcrowded, and have wait lists.
Private clinics are more expensive but are likely cleaner and way less crowded.
For those without insurance plans to cover it, there can be payment plans and payment options. Yes there are state or federal programs insurance programs, like private ones.
But none of the clinics are free.
Maybe there is some private clinic that's subsidized and free, but it really isn't fair to say methadone is free to addicts.