Many people have difficulty creating and respecting healthy boundaries.
Unfortunately, a snowball effect comes into play here. Dysfunctional families that struggle with boundaries tend to raise children that struggle with boundaries, who tend to raise children that struggle with boundaries and so on. In dysfunctional families, boundary violations can range from the erection of impenetrable barriers between family members to a complete disregard for privacy or respect of personal space. Having no boundaries whatsoever is as bad as having boundaries so formidable that they become barriers. Complicating matters even further for the child of a dysfunctional family, these extremes can fluctuate rapidly within the same family, the rules changing frequently and arbitrarily.