Obviously the extreme child abusers isolate their kids from the outside world as much as possible.
And, also obviously, I DO know that not all homeschoolers are abusers or isolate their kids or keep them in a bubble. In fact, I'd wager it's a relatively small percentage.
Public schools and home schooling both have their pros and cons and there is a huge range of people involved in both systems.
The point is, that if you are a parent looking to severely isolate and neglect and abuse your child, home schooling is a tool that makes it easier for you to do so and get away with it.