drinking at work?

I am not sure why people do some of the things they do. Not normal things like brush your teeth in the morning or wear socks with sandals but things that I feel are out of the balance of nature or you know just not done. Am I out of touch with normal human behavior or are people really going off the beaten track? I seem to find myself saying why? seriously why? more and more often lately and I really want to know why. For instance I work in food service and lately I have run into many co-workers who feel like it is okay to drink while working. Now I know food service is not a super hard job and many people could drink and perform the job but you are at work. When I mentioned this to a friend of mine who works in an office she shared a similar experience. People were going to lunch and having a few beers then returning to the office to complete their day. Having worked in an few offices I can see why you would want to drink but again you are at work or returning to work. None of these people were drunk they had just been drinking. So I guess I am wondering why do people feel like it is okay to drink and work?