The only reason I could think of is that alcoholism falls too close to a medical issue, like LadyL said, but OP wasn't asking for medical advice, she was asking for polite responses. But IMHO, the post was much more like someone saying "I have X issue, how do I politely inform people about it / get them to leave me alone?" There have been lots of threads about people with physical or mental illnesses addressing the issue that didn't come too close to giving medical advice, and I don't see how alcoholism is different. Just my two cents -
Maybe it was something else, though?