I have tight, overlapping teeth. I wore neckgear because my dentist said I "needed" it. My teeth are still tight and overlapped (I have a *really* small jaw) and I regret having tried to force them to be otherwise. I have zero doubt that my TMJ has to do with that -- I think the neckgear permanently altered and injured my jaw. I have one child who has tight, overlapping teeth like me and we are not going to do a thing about it. The dentist has said that his bite is fine (as is mine!) and it's just cosmetic. If it bothers him when he's older, he can make the choice to have them worked on then. But he doesn't care now, and I'm not going to assume that his future self would want me to make the choice for him to suffer for prettiness. My husband has pretty unattractive teeth by the usual standards -- they're widely spaced, oddly shaped, grooved and stained. But you know what? He's not in pain like me, and neither of us care that his teeth aren't pretty, and neither of care that my teeth aren't straight. We really, really just don't.
FWIW, I know a guy, middle-aged, who just had his teeth straightened. I can understand why he did it, but when I saw him with his new teeth I was surprised to find that he'd also lost quite a bit of character. Now he just looks like anybody else, very bland. I'm not saying that someone shouldn't fix their teeth to feel better about themselves, just that... it has a lot to do with perspective I guess. Perfection isn't always the most attractive thing.