Similar with people who suck at guitar but own a $3000 Gibson or whatever. I feel like good equipment while you’re bad just makes you look like a joke. Perhaps this is a blue collar ethic though
From the social signaling angle, being clipped in and wearing spandex also says "this ride cannot possibly be for transportation," because it's quite impractical to go anywhere but back to your house dressed like that.
I see it all the time while out hiking. The group of 20/30 somethings who just went to REI, spent $300 on an outfit to go hike 3-4 miles while downing a couple beers. No trail etiquette, only there for the appearance. It's truly wild.
Likewise, the guy who wears ordinary casual clothing on a hike is saying, "let's enjoy the nice place we've walked to," instead of "I'm on an adventure, just look at my gear!"
And to be fair to wheel-runners, it could be that what I'm reading as haughty disregard is actually the same kind of abstraction one sees in foot runners, a kind of meditative absorbtion in the experience of exercise. This might also explain why they appear unable to see stop signs.
I often use a bicycle for transportation, and I've noticed that spandex cyclists won't give me the time of day. This happens even on otherwise deserted streets, where I and the other cyclist are the only two people for a mile. No bell or "on your left" from an overtaking cyclist, no wave of the hand from somebody going the other way, not even an ambiguous nod of the head. It's the strangest thing.
edit: I don't mean to imply that spandex cyclists would actually put bells on their bicycles.