One thing that I learned this year when I wanted to gain some muscle-weight is how much having some physical presence has in the work place. I realized how much more seriously that I've been taken seriously since I'm not this skinny kid on the job. I'm not the only one whose noted that. I've heard of business executives who've taken up bodybuilding just for this reason. In the world of first impressions, looking fit and strong also translates to looking capable of doing the job. I know many people don't want to admit to this but until you experience it, you may not be inclined to believe it.
Being overweight often tells a lot about a person without the person ever saying anything. I remember an obese employee who worked at our shop years ago. He looked kind of slow. That wasn't an illusion. He was incredibly slow because of his obese body. He could only do a fraction of what our more physically fit employees could do in a day. Plus, he was always sick and frequently injured. The book definitely matched the cover. Once again, we may not want to admit it, but it's true that the appearance of physical health and strength (or lack of it) makes a difference at work.
Another incredibly valid reason that has been stated by self defense expert Sammy Franco to look strong is deterrence. It's a known fact that criminals don't typically prey on what looks like a strong person. They go for the seemingly weak and incapable. Deterrence is always best in self defense and walking around looking like a pillar of strength will help keep you safer.
I'll agree all day that modern fitness has taken this drive to look a certain way too far but I don't see the solution to this as completely disregarding looking fit as having any merit. It's all a balance and I don't see the answer to this problem as tipping the balance completely in the other direction. Looking the part still means something.