You should do. Why not require it?: Gee I wonder how it would go if we required instructors to be good examples by abstaining from alcohol and quitting smoking?:shocked2:
As far as alcohol is concerned, it's a pretty wide concept. One thing is having some beers in the evening or a glass (or even two?) of wine at dinner and another thing is an instructor getting smashed every night. There's enough literature on dehydration, physiological effects of alcohol related to gas narcosis and decompression sickness and so on, to know that alcohol and diving don't go together.
Smoking is just stupid. Apart from the obvious incompatibility of smoking and diving (which BTW is mentioned in the OWD course), all Divemasters and Instructors know the risks involved by being a diver and a smoker (Recreational Encyclopedia of Diving, etc). predisposing them to lung over expansion injuries, heart attacks and reducing the capacity of carrying oxygen in the respiratory and cardiovascular systems.
Instructors are supposed to be role models. It shocks me to see instructors who smoke. The agencies should crack down it and not certify dive professionals who smoke. I know they won't but it would be coherent if they did.