Alcohol is regarded as lowering inhibitions, which allows people to express themselves honestly and break down boundaries while returning to the normal social order the next day.
While alcohol does lower inhibitions, it is generally only acceptable after work or at the odd outing/party. A smoke break is acceptable during work and might be the only time different departments and levels from management to floor workers interact on a day to day basis.
smoking was a good social lubricant as well. you can see that in the old Hollywood movies and in real life back when smoking was the social norm.