"The majority of home-schoolers self-identify as evangelical Christians."
Christians homeschool ...and they want creation founded science textbooks! Where's the surprise?!
http://www.crosstalkblog.com/2010/03/ap-does-hit-piece-on-homeschool-texts/
"We're not religious home-schoolers, and there's somewhat of a feeling of being outnumbered," said Perry, who has home-schooled three of her four children after removing her oldest child from a public school because of a health condition.
Perry said she cobbled together her own curriculum after some mainstream publishers told her they would not sell directly to home-schooling parents.
Let me get this straight- mainstream publishers won't sell to homeschool parents, but Christian publishers will, so it's our fault that there is a dearth of secular science texts available on the homeschool market. Is it a Conservative Creation Christian Homeschool Conspiracy? Inquiring minds want to know.
Warning- barely related anecdote: two summers ago I had over 400 textbooks from Hold Rhinehart Winston covering nearly every subject from 6th grade up. My husband met a retiring textbook salesman, and the man gave us the contents of his garage and a rented storage facility. I donated those books left and right, and kept about... 70. 
If non-Christian home schoolers (and i just talked with a couple) want main stream text books there are plenty available through their public school system. As they purchase new texts, their old ones are sold to the public for pennies on the dollar.
...and probably worth every cent. 
Thanks, Aaron. Your response made me smile out loud. Back in the olden days of Christian education when the only Christian school text book was BJU's Physical Science, I taught World History from a public school text book. I'll always remember the chapter entitled "The Reformation Destroys Christian Unity".