Sundays used to be not really a day of rest, but the day all the stores were closed back when I was a kid. We often went to church, then out to lunch, then lolled about the house, but religion wasn’t the reason we went to services. Hell, we didn’t really even do church to worship - I think my mom just wanted the community and the peace, which I can respect. We also occasionally went to temple on Fridays or Saturdays (can’t remember which anymore) since half my family is Jewish.
Sundays were also kind of a lazy day back before my husband and I had kids. I still remember long days of three-hour naps even after sleeping hideously late and having an enormous lunch.
Now that we’ve got children, Sundays are more active than any day of the week. The kids usually wake up at 6:30 or before. We generally take them somewhere fun and keep them active outside the house Saturday, which is actually easier than keeping them at home because it’s more structured and, when we’re out, they’re on their best behavior. But Sundays we like to get things done around the house, which means that the kids need to be directed or they get bored. Bored = crabby as hell. Both kids are in a state of constant motion if they’re not sleeping. I frequently wake up sore on Monday and have started working out almost every day now that they’re older; otherwise I can’t keep up.