When I was in high school, I wanted some tattoos and a nose ring. My dad said no, you'll give people the wrong impression. I said "What impression is that?" He said they'd assume I was on drugs. I said that was their problem, not mine. I sang the teenage party line that appearance shouldn't matter. He asked if I really meant this. I said yes. He said if appearance doesn't matter, then starting tomorrow he would wear biker shorts with a flannel shirt tucked in, and I could do whatever I wanted with myself. I thought it best to not call his bluff. He had a little bit of crazy in his eyes; you don't play chicken with someone like that.
I saw an episode of What Not to Wear a few weeks ago where the girl sang the same tune. She was a recent graduate with a doctorate in Sociology, and she insisted that image is nothing. Stacey said something to the effect of "You're trying to communicate that you don't care about materialism, but what people are actually seeing is that you're sloppy." (I could picture my mom telling me that I looked like I didn't care enough about the people I was going to see to bother putting myself together. She burned my favorite pair of pants. Burned them.) The girl saw the futility of trying to claim that appearance is nothing. She ate her words just like I did.
I don't know why we're so insistent of this notion. It's youth, I suppose; you think you've discovered something that no one else has thought of. Gonna shake up the establishment, teach them a thing or two: what people think about you doesn't matter. I've been noticing recently how much Christian teenagers apply this line of thinking to religion, treating the appearance of evil as insignificant. They make comments that would cause people to assume that they mess around with people of the opposite or the same sex; they pursue godliness but don't want people to know it. They shrug off the dissonance by claiming it's not their problem how they're perceived, it's what's on the inside that counts.
The outside matters. Case in point: my dad once once gave a guy a discount on his car repair because he looked a little punk. I was away from home and he missed me.