When people take jobs in emergency services, health care, etc., there is the expectation that there will be weekends and yes, holidays that they will have to work. In retail, there has been the expectation that unless it's a convenience store, it will be closed on Thanksgiving and Christmas, even if they're open Memorial Day, Fourth of July, Easter, etc.
The outrage over Thanksgiving openings is coming from the "rules change" -- retail workers used to be able to count on having those days off, and now, not only can they not count on it, many will face the loss of their jobs if they refuse to work. So I can understand the reaction of "What's the big deal -- lots of people have to work holidays, like cops and nurses," but it feels like apples and oranges to me, especially for retail workers who have been at it since before the Thanksgiving opening trend started.
When I worked in a nursing home as a teenager, I actually enjoyed working Thanksgiving and Christmas, because I got to help brighten the day for the residents. I worked early shift, so there was still time to celebrate with my family. And because I was living at home, there was no traveling involved to be with family.
A lot of workplaces that are open on holidays bend over backward to give as many people the day off as possible who want it. They have a skeleton staff, they ask for volunteers (in the sense of willing, not unpaid), they schedule everyone for short shifts, they require only those with the least seniority to work (with the understanding that this is a pay-your-dues thing, and next year you may have sufficient seniority to be off), they allow people to request the shifts they want or switch with one another.
I used to work in a convenience store where everyone was required to work a two-hour shift on major holidays. For Christmas I used to ask for morning hours, so those with families could do the Christmas morning ritual, then I could go celebrate with my friends in the afternoon. I didn't always get it, but I worked around it.
I've never heard of going to the movies on Thanksgiving, but that's just me. Going on Christmas Day is huge, though, and I think that's because by the end of the day on the 25th, many people in the U.S. are Christmased out. There's this huge buildup to the 25th that starts before Thanksgiving, and once the presents are opened and dinner consumed, it's "over," and people are desperate to do something that doesn't scream "Christmas!" -- like going to a movie. It may be a Christmas Day tradition, but it's not a "Christmas" tradition, if you get my drift.
But a movie theater is one of those workplaces that could get by with a skeleton staff/willing "volunteers" and not require everyone to work.