Ideally, you're right. Unfortunately, things happen in life. I've had it where I'm happily playing civ and the Mrs comes home asking for a lift carrrying the shopping in, so I had to help her bring it in and put it away, which took 10 minutes.
Some people have kids, so could be half way through a game and baby starts crying or wakes up or something.
What I'm trying to say is this is a long game to get through, and things happen in that time. If I've put 2 hours into a game I'm not going to quit if my Mrs wants help bringing the shopping in, I'm going to help her, leave the game running, and come back to it when I can.