I've been salaried most of my career, so the possibility of working more than 40 hours per week has always been a possibility, but where they usually allowed fewer hours other days to balance it out. I do remember once we had something really special where we were paid extra (even as salaried employees) for coming in on a weekend. My manager told me not to tell anyone else since this was very unusual and they didn't want anyone else to request something similar. Company is long gone so no danger of that now.
I remember back doing contract work - I'd fill in timesheets for exactly 8 hours per day and didn't get paid any holidays. I showed up the week between Christmas and New Years where I had little to do, but they were OK with it since I got paid. My contracting agency's guidelines suggested not entering more than 8 hours a day or weekends, effectively like we were salaried. I never did, although I supposed I could have insisted on exact hours when I worked 11 hours in a day. I'm not sure what their deal was since they would have gotten more money, but it could have been for better relations with the companies they worked with.