It's not all a matter of money. Some children do better in school than at home. Some parents are happier with their kids in school than they would be homeschooling. It's an individual call, and "school choice" also includes the choice to *not* homeschool if the family doesn't think it best.
Many homeschoolers will tell you that homeschooling kids only takes 2 or 3 hours a day --- even less because of so much of what they do in school is a waste -- and from what I've seen much of the time spent in school isn't on actual learning --- so why can't parents who send their kids to school do both? Spend time clarifying homework problems, do real life practical math problems, reading, history, government, science at home even if the kids also spent 6 hours at the school.
I think too much blame is being placed on teachers who have the kids a few hours a day, 5 days a week for maybe 7 months out of the year --- if a child can't perform basic math and graduates without learning to read it's also the parents' fault --- maybe mostly the parents' fault.