The American government has spent a significant amount of time and money taking on drugs such as cocaine and opium. You may have heard about the government's "War on Drugs" (waged by four presidents) and the massive effort of national organizations to tackle America's drug problem. Mostly, the government has targeted its anti-drug efforts on criminalizing drug use. President Reagan's administration, for example, was focused on being "tough" on drug use, handing down punitive measures to prevent it.
The reason why the government feels the use of substances such as cocaine and opium should be controlled is multi-faceted. First, addiction to these substances can be horribly detrimental to one's health. Cocaine has been linked to seizures, lung damage, and serious heart and stomach problems. Long-term use of opioids can cause life-threatening respiratory problems, and an overdose can quickly become deadly. In fact, opioid overdoses are currently a leading cause of death in the United States.
Second, drug use may contribute to the spread of HIV/AIDS. According to the National Institute on Drug Abuse, HIV can be spread from one person to another if they inject drugs and share needles. Drug use can even impair one's judgment, causing them to become less careful about protecting themselves or their intimate partners from an infectious disease.
It's clear that drugs such as cocaine and opioids have had a profound impact on the lives of millions of Americans, and their potentially devastating impact on people's health is likely the strongest driving force behind the government's stance.