As the legalization of the recreational use of marijuana in California and seven other states (plus the District of Columbia) attests, Americans, and those in many other countries, are realizing that the prohibition on drugs has been just as big a failure as was the prohibition on alcohol nearly a century ago. It has been an ineffective means of preventing what some consider to be a vice, and, more importantly, criminalization has robbed people of their liberty (including the freedom to make mistakes), separated families, destroyed career and income prospects and led to increased violence in dangerous black markets — all at tremendous cost to taxpayers.

Not a complete failure. Some are getting very wealthy from the war on drugs.

https://reason.com/2012/04/22/4-industries-getting-rich-off-the-drug-w

Legalizing prostitution would bring it out of the shadows, improving the health and welfare of sex workers and clients alike. Criminalizing it only ensures that it must take place in seedy motel rooms and unsafe back alleys or clients’ vehicles, and precludes both parties from seeking legal protection or recourse in the event of rape, theft or other crimes. Many sex workers have even been victimized by rogue police officers.

https://www.amnesty.org/en/latest/news/2015/08/sex-workers-rights-are-human-rights/