I work with quite a wide variety of children and parents who are either mainstream school or home ed.
There are home educating parents and there are home educating parents.
Some are doing it as a middle finger to society.
Some don't like things like the class sizes, too much homework, pressure to perform in tests (not just GCSE and above), and seemingly arbitrary rules and punishments. They think that mainstream schooling institutionalises children in a way that they aren't happy with.
Some are doing it because their child tried school and didn't cope or thrive there. sometimes it's because of bullying or factors in the child's life outside of school. Sometimes it's because of SEN or other disabilities.
Some can't be arsed, or wildly underestimated what is required of them, the educating adult, or have subscribed to a theory that children are naturally curious and will teach themselves. These tend also to be the parents who don't believe in rules and boundaries for their children.
Some are doing it because they think they can offer their child a better experience of education than they would otherwise get in school. They research what the local authority has to offer home educating families and make use of events, free museum and library admission and resources, tutors, home educating groups, after school clubs, public spaces, their garden, and generally make sure that they consider all aspects of childhood and a child's learning needs, to prepare them well for adulthood and employment. These children generally are prepared for and sit GCSEs, and may or may not enter/re-enter school at some point before then.
I see a huge variety and unique combinations of all of the above, and I have varying levels of sympathy and respect for the various motivations and approaches of the responsible adults.
My children are happily at mainstream school - this is mainly because I cannot afford to home educate. I would have chosen to home educate my children if I'd have had the resources to have been able to do so, and as somebody with teaching experience and qualifications I think I would have done a good job of it. I content myself with giving my children experiences around school that are educational in ways that school can't give them. We grow our own veg, watch wildlife, visit museums a lot. They have done a lot of Brownies and Scouts badges.
I find the idea of compulsory mainstream school attendance deeply disturbing. I think the freedom to choose to educate your children outside of the state school system is and should remain a fundamental human right.