Union Thing?

I made a little bet with myself before I went to the store this morning,the bet was if the pharmacy would have a sign declaring them closed for tomorrow (Labor Day). I won the bet as the sign was in place. It appears the pharmacies all have the Monday holidays off,and therein lies the rub. I don't have a problem with being organized enough to get my prescriptions filled ahead of any holiday closure (so far),but I imagine that isn't true for everyone,and since it is a medically related business it seems like they should be open at least part of the day on holidays. As busy as they always are if nothing else they could use the time to catch up on their work if it was slow. Now to get to my question...is it some kind of union benefit to be closed on the Monday holidays? I have nothing against unions especially since one pays my pension,but I don't see how this is really a good thing for the employees unless they happened to have the days either before or after the holiday off so they could have a long weekend,but since they are open Sundays someone would be working that day anyway,it just seems like an illogical practice.