Why do people relapse from drugs and alcohol after going through rehab?

Because both are highly addictive in some people. It depends on the individual. Some can go through rehab and come out the other end a stronger person and never do drugs or touch another drop of alcohol, but others have an addictive personality and although they really try hard they often will fall back into old habits. When I see people messed up on drugs or alcohol I often wonder what terrible things they may have gone through to make them this way. Is it simply an addictive personality or they are deadening a pain deep within. I feel it's both.