Rehab can be of use for problem drinkers, habitual drinkers, those with alcohol dependence.
My experience leads me to believe, they are of little to no use for the real deal alcoholic.
Having said that, I've never been, but like I said ... I would have heard a 100 stories of people who ended up in AA, who share from the floor, that it never worked for them.
Some of them did 3,4, 5 rehabs.