There is a vast underestimation of the damage caused by prohibition of drugs. Yes, drugs can be dangerous, but by forcing the market underground they become vastly more so.
Limited competition and liability results in terrible quality control. Drugs will often be spiked with more dangerous chemicals. And the potency will be inconsistent, which leads to overdoses and deaths.
The risk of being caught with illegal substances incentivizes dealers and users to carry more dense and potent products. IOW it pays to transport the strongest stuff. This is why marijuana for example, became 10 times stronger after its prohibition, and part of the reason why the illicit drug market has transitioned to cocaine, meth, and then heroin as prohibition has worn on. Likewise, during alcohol prohibition strong liquors shot up to near 90% of the total alcohol market compared to 40% before prohibition.
Because illicit drug contracts are not recognized as legitimate, deals are enforced with violence. Murder rates cascaded after alcohol prohibition was ended, and ballooned after the start of the drug war. Black market drug deals are an easy source of income for gangs who are then better equipped to engage in other violent activities. End the prohibitions, and that income will dry up.
None of this even begins to address the invasion of security and neglect of due process that surrounds drug prohibition. Civil asset forfeitures (seizing money, cars and other valuables suspected of being used in connection with the sale of drugs or other crimes) have been estimated to be more than all private burglaries. Of course there are also the problems of people being locked in a cage for a victimless crime, and the 50,000-80,000 SWAT raids a year, most of which are connected to drugs.
The drug war is not a response to a societal problem. The drug war is the biggest social problem we face.
Related reading and sources:
https://www.cato.org/publications/policy-analysis/alcohol-prohibition-was-failure