Yes, vanity is the driving force behind the swarms of people seeking to regain youth, recreate themselves and capture a dream. While vain people are often criticized for having an attribute seen as frivolous, I wonder if vanity may only be a person's respect for the body that holds the intelligent thought. A pretty picture is certainly more soothing than chaos.
Some get plastic surgery because they feel ugly and/or are embarrassed about the way they look. Not everyone is born good looking, or even average for that matter. If it truly makes someone feel better about themselves, makes them more comfortable and unafraid to leave the house and find what makes them happy, how could that be considered vain?
Plastic surgery is not always about vanity. People that have severe medical conditions often require plastic surgery. Also, it can help the mental health of many. SRS surgery treats GID and most plastic surgery boosts self esteem which supports the mental well being of the person getting it. It really depends on the person.
No, plastic surgery is not just a sign of vanity. While often times plastic surgery is simply aesthetic there are times it has other purposes behind it. A 'nose job' for example can often be a procedure someone gets to repair a deviated septum and so that breathing becomes easier. Even if the root reason for the nose job is vanity it is not the only reason. The same can be said for even breast implants. While vanity, in some form, may be the main reason a woman chooses to have breast enhancement, self-esteem can often improve and help the woman feel better about herself. Whether that is a good reason to have improved self-esteem or not is not the issue but rather that vanity, strictly speaking, isn't the only reason that the surgery happened.
People have many reasons for undergoing plastic surgery. A soldier whose face was disfigured by an IED might have plastic surgery so he is not reminded of his trauma every time he looks in the mirror. This surgery would also affect the reactions that strangers have to his injury, which might benefit his mental health. Other people might have plastic surgery to change their bodies in a way that positively affects their self esteem. Perhaps some people do have plastic surgery because they are vain, but that judgment is so subjective that it's nearly meaningless.