There are levels of insecurity. I think most people think people who get surgery are extremely insecure b/c they go to the extent of getting surgery. Others who don't want surgery are seen as less insecure b/c it doesn't bother them enough to get put to sleep/numbed and cut open just so they can look a certain way.
I don't think crooked teeth are included b/c the mouth is already open & having crooked teeth can be harmful to the health of a person's mouth.
Some people also don't include surgeries to correct things that are deformed or things caused by sicknesses. Like people born with clef lips, or if someone got breast cancer and had to get their real breasts removed and replaced them with fake ones.
Braces are literally no different than cosmetic surgery. Most people get them for aesthetic purposes. You literally wear painful unattractive devices for YEARS to look better. Not only that you must maintain it with retainers. Most plastic surgery heals in 3 to 6 months and outside of normal health practices need no more maintains. So which is more extreme, something I have to do for years to change my appearance or something that takes a few months?
It's just normalize. It's OKAY to want to fix ugly teeth but it's NOT OKAY to want to fix saggy breasts. It's OKAY to be insecure about gaped teeth but NOT OKAY to be insecure about a flat butt. It's just a normalize double standard that honestly doesn't make sense especially when you actually compare time, cost and maintenance.
As far as "levels"...since when is someone who is actually solves issues/ problems seen as less than someone who does nothing about a problem? Some people are just go getters and some people aren't. You never met someone who refused to show certain parts of their body, won't smile for fear of showing their teeth, or constantly puts down their physical appearance? It's common. But those people is LESS insecure than anyone b/c they aren't doing anything to fix it? I don't think so. I think the fact that someone is willing to fix/change something has more to do with personality type then "level" of insecurity.
You can also take into account funds, information and availability. For example, when chicks found out they could get their breasts, butt, etc done their was a flood of people who use to be "okay with how they look" changing things up.
Anyways, I think most people really hate plastic surgery and throw around "insecurities" b/c they see it as cheating and people hate cheaters. They hate to think that someone got something the "easy way." I can respect that argument more than the insecurities bullshyt. Everyone has insecurities so to try to label someone with a very common human emotion in order to shame them is irritating.