Finn was supposedly just a pill taker but we all saw how off the rails he went so it's not like the showrunners aren't aware of the possible consequences.
However, I used to work in the hospitality industry and you'd be amazed how many bartenders are recovering alcoholics. One friend told me the money is just too good to pass up and getting to watch all the ridiculous behavior from his customers helps him stay sober.
I also heard them talk about the differences between clean and sober. In those conversations, clean referred to drugs while sober referred to alcohol. So an alcoholic that smokes pot is sober but not clean and a drinking pill addict is clean but not sober...I know they were splitting hairs, but it was interesting to listen too nonetheless...
