> Most people aren't dying from an accidental overdose

Yes they are. Before fentanyl contaminated heroin came around most heroin overdoses were because of massive differences in product purity. You know the dosage for your usual 10-20% heroin and when you get a batch of 60%+ you are doing over 3 times your usual dose without having a clue and because heroin has a low delta of LD50 to active dose, your usual dose is now letal.

If medical grade heroin was available, with known purity and no contaminants, heroin deaths would drop to almost 0. The drug itself isn't even that distructive in normal dosage, apart from the crippling withdrawl that btw is not letal and dosen't even require hospitalization, unlike benzodiazepine and alcohol withdrawals which can be fatal.