This is an inaccurate understanding of the drug economy. The drug cartels that supply the street dealers are multi billion dollar businesses rivaling the size of the big pharma corporations. And the DEA absolutely is not "usually stopping" them. They disrupt low and mid level arms of their operations with some regularity, but it does little to stem the rivers of money flowing towards the groups controlling the illicit drug trade at a high level.
Even if we presume that big pharma is a very corrupt industry and that allowing advertising of narcotics would increase drug use in some populations, bringing the production and distribution into a moderately well regulated market would likely cause a net reduction of usage and overall harm.
Didn't we kind of already try this out some with opiates? Didn't big pharma already push opiates and cause millions of people to become addicted and cause an untold number of deaths and didn't that contribute to the current situation that we are in now with opiate addiction?
I don't see how legalizing it completely where anyone who wants it without a prescription could possibly turn into anything but an absolute mess. How many millions of people will say "O, the government legalized it and I can buy it in a store, it must not be so bad, I might as well try it out", become addicted and have their lives ruined? People can't rationalize their way out of addiction of this stuff easily.
Not exactly, hence the rise of fentanyl. Prior to the rise of fentanyl, new addicts often went from prescription pills like oxycodone to heroin as their lives unraveled because prescription drugs are expensive and hard to get. Some enterprising drug dealers started enhancing their cut heroin with fentanyl which can be imported from China and is extremely dense compared to other opiates, which matters because smuggling is most of the cost. Downward pressure on the prices changed the ratio until you were left with pure fentanyl, so in effect prescription pills were not available enough and drug dealers were able to capture the market with more dangerous but cheaper product.
Even if we presume that big pharma is a very corrupt industry and that allowing advertising of narcotics would increase drug use in some populations, bringing the production and distribution into a moderately well regulated market would likely cause a net reduction of usage and overall harm.