Perhaps they couldn’t afford their lifestyles without the “free” school.
My wife was a stay at home mom.
Yea, we lived pretty frugally but it was worth every penny. Now that we don’t need to, we still do.
We found that home schooling was actually cheaper on the budget than public school would have been.
Even with four kids. we never spent more than $1500 a year.
But we never had to spend $150 each on the school supplies list, pay extra fees for anything or get them a new wardrobe every year.
As they got older, they did do some extra activities but none were very expensive.
They turned out pretty good and include being a copy editor at a Christian publisher and an Astronautical Engineer at NASA. All are living on their own.