Sometimes parents can make their kids feel too pressured. Teens like to feel older and mature, and to figure things out on their own. I think this helps a kid become more intelligent and more confident. A teen is never going to learn anything about him or herself if the parents just do everything or figure everything out for them. They may not ever think that they are pressuring their kid but in some cases they are.
Parents believe they always have the right answers.
Another problem is teens' appearance. A parent will see their kid dressing differently so they think they are gonna act differently. In my opinion that is a kid just exploring other options in life, which is healthy. I don't think it's all wrong for a parent to assume things about their child. They do it because they're worried and don't want anything to happen to their child, which is the most precious thing in the world to them.