Why home-schooling?

First and foremost because it is my responsibility to raise my child. As I understand my responsibility, I am to do all for my child that I can do effectively. If it is clearly the case that someone other than myself can do significantly better, then I can farm that out to someone else; otherwise it's my responsibility.

My child's health is my responsibility. I am their primary care provider for medical needs. When their medical needs clearly exceed my competence, I take them to the doctor. Except in rare cases, this will be rare, for very few health problems require such measures. For the vast majority of medical needs--certainly day-to-day needs--I am competent to provide them, so I must do so and am amiss if I do not. Even if I could afford it, if I were to have a private nurse on hand to apply Band-aids(tm) and spray Solarcane(tm) on sunburns or take splinters out, I would not be doing my parental duty to be my child's primary care provider and nurturer.

Likewise, my child's education is my responsibility. I am their primary educator. When their educational needs clearly exceed my competence, I will take them to a tutor. Except in rare cases, this will be rare, for very few educational needs require such measures. For the vast majority of educational needs--certainly the day-to-day needs--I am competent to provide them, so I must do so and am amiss if I do not. Even if I could afford it, if I were to have a private tutor on hand to teach how to read or write or do arithmatic, I would not be doing my parental duty to be my child's primary educator and nurturer.

The analogy is not exact (that's why it's called an analogy) but I find it highly suggestive. It is part of an endeavor to express one of the positive reasons behind home-schooling and contradict the charge that home-schoolers only have negative motivation.