Plastic surgery does not only enhance a person's physical appearance, but can also have a great impact on how that individual perceives him or herself. This enhanced appearance leads to higher confidence levels, as confidence correlates with one's outward appearance. This improved confidence could in turn lead to better relationships, due to the fact that the individual now feels more comfortable with themselves.
What's the point? It was originally invented for soldiers who had say, lost a nose to the war. Confidence, as Kiwi3004 says, is the main purpose of plastic surgery- but should confidence depend on an expensive, often unnatural looking bit of surgery? I personally find most people who have used plastic surgery look rather ugly, and unnatural.
I just realized- Kiwi3004, you must be a New Zealander! That means the first two responses to the question are both from New Zealanders.