Many things considered 'good manners' are things people with too much money and time on their hands came up with to further distinguish themselves and make themselves feel superior to the rest of their fellow mankind. So much rubbish.
I mean, fancy attire is fancy because it's expensive. Silks, dyes, embroidery etc, that all costed much more. Flaunting ones wealth which was power when the traditions started up. If you're asking after fashion, that's a whole other thing.