I can see how the home schooling curricula providers may skirt around this because many home schooling families are home schooling purely because they want their children to grow up not exposed to theories like Evolution etc - it would be bad for business ( and these people are not doing this for fun, right?). Better for them to let sleeping dogs lie and let the individual families decide on their own than risk upsetting their customer bases.
I agree with everything else you said but this. There is such a wide and varied world populace of homeschoolers now that this is really not the average anymore. Even here in South Africa the mix of reasons for choosing homeschooling as an educational option are so diverse that I think you would have a hard time trying to decide on the "main reason".
Also, the variety of family types who homeschool are just not quantifiable by a specific imaginary stereotype. People that choose this educational path vary from professionals (doctors, teachers, lawyers) through to seasonal workers who move around a lot. You get those who homeschool because their kid struggles, because he is moving too quickly, because they want less pressure for their child and because their child is an aspiring actor/sportsperson. Some choose it because they live too far out, because there is no school that caters to their child's learning style and for allergies or health issues.
Yes there are those who choose to homeschool to avoid (or to push) certain topics, and there are those who do it to provide a wider variety of topics and learning opportunities as well. You just cannot make a blanket statement like this about what is arguably the world's fastest growing learning style without annoying those of us who are choosing this path for our own varied reasons.
And I have found that many curriculum providers DID start out as someone wanting to make a discernable difference in education - that it grew into a business model that supports hundred of various curriculum and support providers is just further proof of the invalidity of your statement.