I also think it can (and I'm not by any means saying this is always the case) cause an unhealthy and co-dependent relationship to form between parent and child that have spent 90% of their time together for 18 years.
Part of the philosophy behind Home Education is to rear a happy, independent and confident child. I agree that at a younger age a parent would be present for a large percentage of time, however the child tends to spend a lot of his/her time with other children, sometimes directed by other adults. Over the years we have attended various HE organised activities: gymnastics, forest school, sailing, mad science workshops, ice-skating, swimming, skiing, chess clubs, board-games day, hall meetings, educational trips... On top of the HE activities ds has also attended after school activities such as swimming, skating, ice hockey and music lessons and cadets.
Now that is older (14), I just drop him off at his various activities and he makes his own arrangements to meet his friends.
What if your own pace is pretty lazy?
Children are by nature inquisitive, a home-educator would use such nature to encourage and engage.
And how do you learn that to get to a great level, you often need to learn the boring bits first? Days before we officially began HE, ds and I had a 'practice' day (inset day at school); the day after ds told his teacher that she was 'so boring compared to mum'. I believe it is my role as an educator to teach the boring bits as pleasantly as possible.
However, school is meant to educate in the broader sense and that means that pupils learn how to deal with different children from different backgrounds, the ability to compromise, hierarchical structures and how to deal with them etc etc.
Why on earth would a home educated child not learn all of the above?
The home education community is just as varied as the school community; home educated children are still taught to respect one another, no matter the background, age or ability; they still learn social rules such as taking turns, sharing, no hitting, etc., being more tolerant of younger ones and compassionate towards those in need; they are still able to accept and follow instructions; they are capable of working independently as well as in a group...
The other problem is that the lessons often go where the pupil wants them to. Why would it be a problem? That is exactly how it worked in my school: on its brochure, it was called 'emphasis on self-directed learning'. Most of us attended university. The ability to direct a conversation (lesson) is an important skill in life, used in a variety of scenarios, from interview to leadership.
I enjoy when my ds (14) leads the 'lessons', as it means he is engrossed in the subject(s): he will be teaching me, showing me, asking multiple questions, researching, discussing, making connections, inventing... It would make for a very boring day if all we ever did was reading the textbooks -which, of course, he does study as he is preparing for his exams.