Hunter style is heavily influenced by teenage girls who are able to see and care about minute differences in style that few adults would care about. Teen girls compete on every metric, not just in the show ring, and are quite capable of ganging up on a frenemy who is winning ribbons and shaming her into tears about her helmet, her hair, or the car her mother drives.
Ironically, hunters is as rule bound and conventional in dress as dressage, and you still have tweens obsessing over whether they will lose points from wearing the wrong brand of beige breech or black helmet.
Also teens are still growing and need to get new clothes constantly. So they have more opportunities to replace things.
Adult dressage riders are not teen girls, and if you don’t have a big weight gain or loss, your gear will last for years, even decades. At the same time, adults often have the money and freedom to please themselves, and no adult really enjoys wearing skin tight white pants 
As far as thinking of a discipline as a club, withhold judgement until you are participating. At the local schooling show level it is no different in atmosphere than the equivalent h/j day or flat class show.
I don’t love how I look in black and white dressage turnout. But I do love being able to put together a passable outfit in which I look like everyone else. I don’t need to worry that I am drawing attention to myself by my high-style choices or conversely by any unusual or inappropriate choices. I want to look workman-like, if that makes sense.
I do not ride a warm blood, don’t plan to. I also follow a somewhat different training program to most local riders. I don’t feel a need to also stand out from my colour choices. Quite the opposite, I want to blend in.