They may not think they have a problem with it and can quit drinking any time, but when they drink, they cannot stop before they get drunk. Abusing alcohol is not something people do because they are bad or weak. It is a disease that can be passed down from a parent or even a grandparent who also was an alcoholic. You may just drink a lot of alcohol without being a real alcoholic, but if you continue to abuse alcohol, you can become one. Alcohol abuse grows worse over time.
Some people die from it.
A relapse doesn't mean treatment has failed. Sometimes a relapse convinces the alcoholic that to stop drinking alcohol is the only choice. Remember, a person who is about to start drinking again usually thinks or talks about drinking before doing it again. That is a warning sign that the person needs to go back to the sources of help listed above.