The three distinct parenting styles described by Diana Baumrind resonate within all of us--we're all aware of how restrictive or lenient our own parents were, but we have also witnessed friends' parenting styles and even strangers on the street or in restaurants. And as much as we would like to impose our own beliefs on a parent with a screaming child in the aisles of a grocery store, we cannot understand their specific parent/child dynamic and should try not to pass any judgment on their parenting style. My own parents were authoritative when I was younger, but have become more permissive as I have grown. I am extremely grateful to have had structure when I needed it but also the space to become the person I want to be instead of who they want me to be. Over the years, I've experienced my friends' parents authoritarian styles and while structure is beneficial to growing minds, it seems to me that the tighter their grip on the child, the faster they'll run in the opposite direction. Just ask the most popular authoritarian parent, "Tiger Mother" Amy Chua, about her extreme confidence and vigor in restricting her daughters' behavior. She is proud to have called her girls awful names like "garbage" and "pathetic", which is considered borderline verbal abuse in the US, but is commonplace in Asian households. So, even though we may not agree with her methods of parenting, we must accept that all families are different and only they can decide how to best mold their children.
Here's a link to an article about the Tiger Mother, it's fascinating and unnerving at the same time: http://online.wsj.com/article/SB10001424052748704111504576059713528698754.html
I feel you bring up an excellent point in acknowledging that parenting styles and expectations are not universal. What is done in one culture may seem harsh in another cultures practices but many cultural practices persist because it is what is thought to mold their children into proper adults in that area.