My friend (and one of my favorite people) has the most beautiful explanation for why she chooses to homeschool. I could not find words to say it better so I'll just let you read what she has to say in her post "How She Learns."
Unschooling for us means we are leading a life that enriches our children and creates opportunities for natural learning. I firmly believe that the most important thing for anyone to learn is HOW to learn; the rest will flow from that knowledge.
Letting go of traditional ideas about learning hasn't been easy but it has been an adventure!