Good point, Chuck! Yes, almost all of the above days have some form of traditional celebration -- cards, candy and fancy dinners on Valentine's Day, wearing green and celebrating Irish culture on St. Patrick's, costumes and trick-or-treating on Halloween, etc. But not all are national holidays.
Chuck would be familiar with national holidays, of course, because banks are closed. Newspaper reporters have to work, or at least a few on any given holiday. Usually, people volunteer to work on holidays, either to be cooperative or because on holidays we'd get eight hours pay for five-hour shifts.
I've always had all holidays off work, which I've always been very greatful for, esp when my son was little.
When I worked at the hospital, OTs weren't considered essential, so while most of the staff of course had to work, me and my colleagues were off.
For the most of my working life though, I worked in a public clinic, they are always closed on a holiday.