1) because I don't like busy work, and would have sent back homework undone.
2) DH has a crazy schedule, so it allows the kids to see him
3) the teachers would dislike me, which would make my kids school time difficult (see #1)
4) I skipped a number of grades myself, and don't see the point in much of it
5) I want my kids to learn how to think, to analyze information, not just do something because they are told
6) I'm too lazy to deal with a school system that I wasn't willing to work in (I considered teaching, thinking those who CAN should teach, I ran away)
7) NOW, we have a dyslexic child. There is no way the school would be able to provide the support and instruction I can provide. Instead of having a terrible self image, etc, my DD knows her issues, we joke about them, make necessary accommodations, and move on.
8) I think the push to do things at a younger and younger age burns them out, and also teaches to be automatons....do it this way, at this age, and meet XYZ requirements. Sometimes a book shouldn't be read in 7th grade, but when the person is old enough to actually understand! Maybe they don't need to write book reports until much older.
I guess that's enough reasons. :-)