In America, most people want to look good and to feel good. It's not narcissism so much as it is a cultural standard and a cultural expectation. Nobody likes to look in the mirror nude and think "I look like a mess," or to go on an adventure and feel tired.
It seems to me that decent, spirited people always aspire to improve their souls, their brains and knowledge, their fitness, their appearance, their skills, their morals, their relationships, etc. etc. Giving up is not cool and shows no respect for God's gifts - and surely nobody wants their teeth to indicate that they might be from England or Bosnia.
Orthodontia in America: America’s obsession with perfecting its teeth.