A child who is homeschooled compared to attending a school meet so much fewer people in their lives - all else kept equal; This means they're more likely to be socially awkward when they grow up. How to compensate for that?
An easy example of this might be to take advantage of guided tours of theatres or museums. It's not often easy to get a guide for one parent and one child, but organizations will accommodate a group of 30 more frequently. Another example of this collaboration is electives. Even the best-intentioned homeschooling parent might not know some skill their children have taken an interest in (e.g. cartooning), but if another homeschooling parent knows that skill (e.g. a professional cartoonist), it's common for such parents to make arrangements for lessons in the interest of the group. A parent with an interesting hobby (e.g. model rocketry or electronics) could very easily expose other children to that hobby in an educational way. A group of willing parents can go a long way towards replicating the breadth of educational experience that a traditional school and its resources can provide, without any of the drawbacks.
It wasn't that long ago that people grew up, went to school and worked in the same neighborhood always dealing with the same people. They rarely traveled and moving was unheard of. Did these people grow up socially awkward? No.
Home schoolers are in little league, pee wee football and quite often a very large religious community.
Being home schooled doesn't cut you off from the world.
With all the failings of the school system, home-schooling still remains a fuck-you to the humankind -- like some BS bubble created by the kid's parents is inherently better.
In school, everyone around you is the same age, you can't avoid the dickheads no matter how much you might want to, and they can harass you with near impunity.
I realize that some allowances must be made for children (can't give a 10-year-old total control over their lives the way an adult has it, after all), but the massive differences in something that's supposed to be preparing them for adulthood are a bit crazy.