Is this fair for 4 friends to do?

Okay so we are in a carpool. I was out today. My mom picks up everyday after school. Then the one day she can't, no one else's parents "can pick them up" so my mom is forced to leave work and not get paid to pick these "friends" up. I was home sick and my dad was in NY for work. It just pisses me off that every single day my mom picks them up and when she can't she still does. I don't feel this is fair, I need other opinions.