I am glad you recognize that homeschooling is not an option (nor would it likely be the preferable option from society's standpoint) for all children.
As a public school teacher, I don't get to meet the parents of all of my students. Some parents either aren't concerned enough or possibly unable due to work commitments to come meet the teachers on the several occasions we provide for that purpose. They also don't schedule conferences at other times.
From my limited experience with parents, however, I've noticed that unconventionally dressed students generally have unconventional parents, and conservatively dressed parents usually have conservatively dressed children.
It seems likely to me that parents who are very concerned about and involved with their children are more likely to homeschool than those who are not, and I'd suspect that the percentage of concerned parents who homeschool might depend upon the perceived quality of the local school system as well.