- They legitimately love their jobs and the kids.

- If they quit/are fired, and have to find a new job that may reset their steps (i.e. they take a pay cut, but not just for one year but for their career). Inter-district transfers can be blocked or have the same problems at the receiving school.

Plus there are some fields that are more in-demand than others (e.g. maths/science Vs. art/social studies).