Homeschoolers teach their own children for a variety of reasons. Traditionally, most homeschoolers were conservative Christians who did not want their children to be exposed to immorality or doctrine that contradicted their own, or who wanted a more religious education. Today, many parents homeschool because they want their children to get a better education than they can get from the public schools. Others have children with special needs that were not being met by the schools. Some families live unconventional lifestyles, travel or move often, and homeschooling makes these choices easier.
Some children are performers and homeschooling fits their schedules better.
I'm as qualified as anyone else, and maybe more so. First, many public school teachers are not certified teachers. They are teaching on emergency credentials. Many are not certified in the subjects they teach. Certification doesn't make a teacher qualified.