When you start using eg meth, you open up, with reasonable probability, a whole host of other externalities beyond impaired driving. (The same is true of alcohol, except with far lower probability, which is a key disanalogy.) Hard drug users commit property crimes and violent crimes at a much higher rate than people who don’t use. Crime increases during binges, suggesting causality. But you really don’t really need academic study to demonstrate causality here - it’s obvious that people steal to fund addiction.

And yes, you can prosecute them for whatever property or violent crimes they commit, but for the victim, it’s too late! They have already suffered. A better outcome is if we decrease the amount of usage of drugs like meth and fentanyl via law enforcement, and subsequently decrease the externalities that society has to bear.