In many cases, those committing these types of offenses need help and support rather than shunning.
Also, from my best recollection, alcoholics cannot be disfellowshipped. Alcoholism has been determined to be a disease, and the Society would take a lot of flak for throwing out someone with a medical condition. Besides, it seems to me that an awful lot of JW's like liquor more than just a little.
Again, this goes back to what I've said in previous posts. Elders should have some sort of psychological training so that they could help some of these "sinners". Throwing people out does nothing to help them....rather it solidifies their feelings of inadequacy and their low self-esteem.
Obviously, a person who is committing these types of acts should not be in a position of authority in the congregation, but shunning them or labelling them by reproof and then letting them deal with it on their own does NOTHING to help heal the person.
It's a complicated issue, but it seems that the Society is first and foremost concerned with how they look to the "world". The individual's spiritual life and their problems are of little relevance to the WTBTS.
I've also noticed that disfellowshipping is based very frequently on personalities and prestige. There was a pioneer sister in our congregation who was frequently drunk, involved in hit-and-run accidents, and openly lewd behavior toward the unbelieving husbands of many sisters. She was never disfellowshipped, nor even reproved, and she maintained her position as a pioneer. In fact, she was frequently used in assembly programs.
Then there was the MS who was married to the daughter of an elder. He is still in prison for a murder he committed while trying to get money to support his cocaine habit. I never heard a word about his being disfellowshipped from the congregation, and to the best of my knowledge, he was not.