To make a difference :shrug:
That's a nice warm fuzzy goal, but the reality is if you work a 9-5 job, you have to take off work a minimum of once per month to attend a board meeting. That's fine for some, but a lot of employers aren't too understanding about their employees taking on an obligation that they KNOW will take them out of the office like that. Then, BOE members must also spend some time in their offices, doing the practical duties of the job, making phone calls, reading proposals, etc. Then there's one board meeting a month that is in the evening. Then there is a certain expectation that members put in appearances at school functions like graduations, school concerts, special events, etc. Some of these are during the day, some during the evening.
Many of the Board members sign on "to make a difference" because they have children in the school system and they see ways they think it can be improved. But because they have children, they have afterschool activities as well, which may or may not conflict with all those special events, evening meetings, time in the office etc.
It's all well and good to want to make a difference, but the reality is that it's not practical for $4000 a year. That's why these candidates run unopposed and when there is the occasional newbie getting elected to the board, many of them are in for one term and disappear.