Drinking on the job doesn't mean getting tipsy or hammered on the job. Many people can handle 1 beer or a glass of wine with a meal just fine. But, not all bodies react the same to alcohol, and not everyone eats the same, and more importantly, not everyone can exercise moderation and stop at enough drinks to not be a hazard on the job.

It takes one person having one too many for whichever reason for a preventable accident to happen. There are certain jobs where zero tolerance is the best policy, imo. I don't want to worry about whether my colleague handling the big-ass knives or driving the forklift half a meter away from me is tipsy or not.