Let me preface this by saying you are all individuals with your own agendas so train how ever you want.
But the reality is even people who are unfamiliar with Bodybuilding, anthropomorphics, aesthetics, symmetry etc. can see a major imbalance in some one who is built like a light bulb.
In general society admire strength and fitness and yes if you have a well developed upper body you may be more highly regarded than the skinny guy but if you have overall developemnt you will be more highly regarde than the guy with pencil legs and a strong upper body.
This in no way means society thinks because you decided that training legs was just to damn hard that lack of leg developement is preferred over a well developed upper body.
Women don't stand around saying "hey Debbie check out the under developed legs and flat ass on that guy!"
But they sure as hell say "Wow did you see the butt on that guy!" Or "Your husband has nice legs"
If you have never heard comments like these you have no experiance with women.
Top heavy physiques with no leg developement look ridiculous and make you a laughing stock to those of us understand the importance to leg training.
If you think that haveing a well developed upper body and skinny legs is not off putting you are wrong.
Case in point facility I train at has to pools indoor outdoor. Lots of younf guys workout there they all wear those ridiculously long shorts you know the ones where you look at them and think if your shorts are that long why not just wear pants.
Anyway at least a few of them wear regulat bathing suits when they go out to the pools and I gotta tell you when those knuckle heads come strutting through the doors with their pumped up arems and chests and the shapeles little under pinnings they are laughed at and the girls are pretty harsh as well maybe they do not say confrontational things but they giggle and dog these guys.
Its really funny because these upper body guys are oblivious they just either don't care or really think no one notices. And they are not being laughed at cause they have big muscles, myself and several other menbers who may be out there on those days are also obviously barbell boys only we are a little more balanced we might not be the ideal to everyone but we don't get laughed at either.
while I absolutely respect a persons right to train however they please. I know for a fact human being instictually find aesthetics more pleasing to the eye.
I also from my own experiance find most people simply don't train legs because they don't have the heart for it. Because its just to much hard work.
Case in point you never hear people running around telling everybody why they train legs. But you will forever and a day hear people running around telling people why they don't.