It takes a while for a doctor or hospital to catch on to what is going on.
How many patients do they have? How can they be expected to keep track of everything every single patient says? Especially an addict, who is of course downplaying the whole thing, so when the doctor opens the chart, it is going to say, So-and-so came in talking about drinking a couple times a month (yeah right), and then six months later, it is going to say exactly the same thing.
I totally agree that doctors don't know as much about addiction as they should. Really, they are the ones to blame for the whole prescription pill addiction thing. If they would just recognize a drug seeker, they wouldn't give them their pills and there you go, no one would have any and they would all have to go to rehab. But at the same time, a doctor cannot accurately diagnose any issue without the right information. And the addict is manipulating them just like anyone else, into thinking there is nothing wrong with them. Since a doctor does not see them as often as a family member, the manipulation continues a lot longer until the doctor realizes there is something wrong.