An extrinsic reward that I think about is the summer time. The summer is a time that families can get together. It is also a break for the teachers to be ready for the next year. Teaching is a calling more than a social service. Someone has got to be called to teach.
Teaching is also a passion one has.
Teachers love their job or they would not do it. If someone is called to teach then it is for the right reason but if someone just says they are going to teach because they do not have anything else to do then it is for the wrong reason and they are not going to enjoy it.