People are simply victims of their addiction. Addictions are often excuses for unacceptable behavior. The second answer is deeper. Addiction is idolatry. Everyone who chooses something other than the Lord as the top priority in life is addicted to that idol.
Addiction is so popular because idolatry is as popular today as it was in biblical times.
This understanding of the problem suggests an effective response. When Jesus walked the earth, He could heal any disease that a person asked Him to heal. Faith healings of physical illnesses occur today with less frequency, but faith healings of addictions are still commonplace. Faith is so powerful because God is the key ingredient in recovery from addictions. However, even they need to do a lot of work to get free from the shadow of death.