Is "personal hygiene" something you do for yourself, Jack? The answer, in most cases, is no. We "take care of ourselves", to impress others. We care about the impression we leave on others. We wear deodorant, because we don't want other to think that we smell funny. We comb our hair, so others won't make fun of it. We iron our shirts for the same reason, and so on.
If it's Sunday, and you are just going to lay on the couch all day, do you always take a shower, and comb your hair? You know you are a liar if you say you always have/do! It's not the same as presenting yourself to others.
Fading custom? No doubt about it. Just like many others. Take a man holding a door for a woman, or offering his seat in a crowded room, or a bus/train. But, IMO, a suit will always look nicer than a guy in a polo shirt, same way a Caddy will look nicer than a Taurus.
And if your tie is killing you in the 90 degree heat, your collar is probably too tight, and it's not a tie issue at all.