In the US.
Every job I've had feels entitled to all of my time no matter what I've agreed to sell. I've had jobs force me in only for me to sit around with nothing to do. It's not that I wasn't being paid or anything, but the expectation that I'm supposed to drop everything in my life at the drop of a hat is indicative of one thing: they think their money is more important your life because you agreed to work for them. They feel they own you and when you're one missed paycheck away from homelessness and there's nothing stopping them from firing you at any point, they legally do.