I didn't mean that anyone's social anxiety is caused by parents not teaching social skills. I mean that for average people, without any particular anxiety disorders, there are a lot of parents who think that kids learn social skills by osmosis. There has to be some direct teaching here.
I know that these disorders are things people are born with; it's not the same as kids who think it's OK to be rude, bully, have no manners while eating, make racist remarks, etc. These are things that parents have a responsibility to model.
If a child has noticeable social anxiety, there are things that parents can do to help; therapy, social skills groups, medication. I have seen wonderful outcomes when kids got the help they needed. I just wish parents would pay attention to their kids and notice when there is an issue that could make life difficult for the child.