1) I'm a homeschool graduate. I've never attended school myself so home education seems perfectly normal to me. It's my "default" option in the same way that most people assume their children will go to a school like they did unless they had a particularly bad experience.
2) Not only is homeschooling normal to me, but I enjoyed it! I have many fond memories of childhood and often they involve something related to homeschooling. I can say from experience that it can be a wonderful way to grow up.
3) I'm uncomfortable sending my young children to school when I have no experience with it myself. As someone on the outside looking in it looks strange and unpleasant.
4) I enjoy the freedom homeschooling provides. I don't have to make our lives work around the school's schedule. We can get up when we see fit, stay up late without it being an issue the following day, vacation at any time of year we wish, take advantage of places not being packed with people on the weekdays, etc. Our family will be going on vacation this year on September 8th...which is only a few days after school in our area starts! Another big freedom for us is not having to consider the school district when we choose where to live. If we purchase a home in an area with not-so-great schools it doesn't matter. I would hate to pass up on a house I loved just because of the way the school districts are drawn up!
5) I'm not impressed with what I've seen come out of the schools in my area. I've worked with a number of people who seriously should not have been able to graduate highschool based on their skills or knowledge. Our local schools don't seem to be preparing young people for day to day life AT ALL.
6) I appreciate being able to tailor our experience to my children's needs and interests. We follow a child-led path which would not be possible if they attended a public school.
7) I believe that homeschoolers have a much better social experience than children in school. Schools are not meant to be a child's only social outlet, yet many parents expect them to be. Homeschoolers can have a much more full and varied social life, in my opinion.
8) Safety. After reading a news report about a teacher feeding his own semen to his students in cookies....yeah....not happening! Our local schools also do not have a particularly good reputation with violence, etc.
9) Time. Life, particularly childhood, is too short to spend most of your day in school.
And...quite a few others, but those are my main reasons.