Yes and no. So no people don't believe appearance is everything, the only time that's true, is when you just see someone walking by etc, because the outside is all you see. But that's also where it gets tricky. The outside is the first you see, while we all have a different view of physical beauty, the fact is that we are attracted to those that fit what you believe to be attractive. So personality etc plays no role.
When someone is insecure, getting positive attention is definitely a plus. Now you can be the nicest person, but how many people are gonna walk upto a girl and say "damn girl, you are stunning" or whatever, well only those who think you are attractive. So when you're not, that's gonna make your self-esteem go to absolute zero.
Obviously there is much more pressure on women than on men, our society is focussed mostly on the beauty of women. Still that doesn't mean men don't get insecure. If you are trying to pick up a girl that you find physically attractive, yet you are not, you will get rejected a lot, causing your insecurity to grow and eventually you are too scared to ask a girl out.
Simple fact is that in life we want to fit in, even people who claim to not want to fit in, want to fit in. Emo's hanging out with emo's and than saying they don't want to be different, are proof that they don't actually want to be different, they want to rebel, or feel like they don't fit in with certain groups. But in the end we all want to fit in somewhere. Our outside decides a lot of that, it decides how popular you are yes, how easily you can get into a relationship etc etc. But it's also definitely about how you feel about yourself.
In the end the majority cares a lot about appearance, however luckily most do not choose surgery to change it, but trust me, finding a woman below 30-35 who's truly secure about how she looks, is pretty much impossible, even if she says she secure, trust me that nose that's a little bend, or those lips who are just not full enough, those breasts who should just be a size bigger etc etc.
This is also why they keep using make-up, it's why so many women buy bra's that push them up, fill them up etc, just to make them appear more feminine.
Insecurity dominates us, and I would say that physical appearance is the number 1 reason.

