I agree with the above post by Glitter. You are a friendly kind face to them and sounds like your co-workers are nice too. Maybe you are in the right place after all.
We had a pub and the early morning people would come in for "the cure".
My mother was very kind to them and would give them tea and talk to them. They never objected. Just thinking, maybe Al Anon would be good for you. The 3 Cs etc.
I do think that these people are in a very sad cycle of addiction. It is not a choice per se.
They may or may not get the desire to stop and seek help. It is not like deciding to eat too many rice crispies. Oh, if it were that simple. Keep yourself tuned and you can keep working there. In this economic climate, a steady job that you like is a good thing.