Dress varies by location and culture. It's always been that way. Norms change but not that much, really. It's all about dressing for the norm, wherever you might be. Most of the USA is very hot in the summer and people wear shorts and light clothing as much as possible.
Some people are just slobs and cannot look presentable no matter what. Someone can look very presentable in shorts and a golf shirt if their clothes are clean and they practice good personal hygiene. Here in Los Angeles, I can go almost anywhere dressed this way. In Malibu, even at Nobu, it's unlikely to see anyone wearing a suit, ever.
Growing up, my dad wore a nice suit and tie everyday to work. He was a lawyer and it was the norm in his professional world. He was always well dressed even when not working, quality shirts and sweaters, nice shoes, etc. I try to be presentable even in my extremely informal world, which means looking in a mirror before leaving home and wearing clean shirts and shorts or jeans. One thing I've unfortunately had to come to grips with is that what you can get away with @ 25 or 30, (anything), can look pathetic on an older guy. That worn out t-shirt and ball cap that was ok then makes you look homeless in your 50s.
It's obvious by looking around that some people just throw in the towel on their looks in middle age, (if they ever cared), but anyone can look presentable for others. Not talking about extreme vanity, (which makes people look like a fool, IMO), just clean clothes and hygiene, etc.
