Not my experience whatsoever. Philadelphia public school growing up, we had young white kids who would have unambiguously fallen into categories of "Punk" "metalhead" "goth" "hood" to just name a few of the most cliched highschool-sitcom-but-actually groups. (there was even regular assertions that "hipster" and "scene" were different but that one never really grokked for me)
Especially having lived east vs. west coast over the last decade, the assertion that there isn't a distinct subculture in a non-derogatory way that can be defined usefully as "hipster" doesn't ring true for me.
And for the most part, even growing up, I never got the sense the grouping was malicious except in rare cases. Most kids would own their tastes (usually associated with music and dress) and would probably take insult if you confused their clique :P (And less in the "you just shit on me" way, but that could happen, more in the "how the hell could you confuse that" fashion, which implies to me that others saw the same clean voluntary-group-agglomeration that I saw.)
Where I'm from it's basically "emo-style clothing but with colored hair and eccentric outfits". Just search for "scene hair" online to get an idea of the aesthetic. "Scene/emo" tends to be the description for a lot of scene or emo aesthetics and never "scene/hipster".
Tangent on the whole emo discussion, I recently heard of "Midwest Emo Revival" after the "popular" emo subculture kinda faded from the coasts. Makes me wonder how different other subcultures can become when the popularity shifts regions or the "underground scene" gains more popularity.
Re: subculture shifts and underground revivals, don't even get me started. I have a personal fascination in how what "goth" is has changed _so drastically_ over the last 30 years, (The Cure, david lynch/oingo boingo, then the explosion into cybergoth/punk, overlap with death metal, branches off into classical) Someday I'd love to read on someone who has made a study over how these shifts occur and propagate, largely with an eye for how technology has changed this in a post-internet age.
Pragmatically, because they often _wanted_ to and designed their personas intentionally.
You seem to be arguing that visible signifiers of subcultures don't provide meaningful signal. I would disagree broadly, and specifically in that the I don't even consider "hipster" the "generic white dude." Beanies? plaid? At least where I grew up those were _very conscious statements_ and not just the median type of dress.
As you say there are people who present as one thing who have tastes otherwise. I present nowadays as a metalhead but spend far more of my time listening to hip hop. But if someone called me a metalhead I'd probably go "there's some truth in that" and understand the connotations even if it's not 100%, and I see hipster similarly, whereas you seem to find it to have no signal whatsoever.
The core of our difference seems to be whether "generic white dude" falls into hipster. I simply can't find that to be true. The aspects the wikipedia article call out, I've only found to be "norm" in places that would, again without malice, probably self-identify as "hipster", although there's a definite "grunge" overlap. (Seattle, Portland, Vermont, in my personal experience) My main point being, that does not even come close to describing the vast bulk of jeans wearing boring-tshirt-or-button down blue/white-collar loafer/sneaker wearing white dude that I've met over the course of my life. (And sanity checking myself with a glance down my 55 person teamroom :P)
This may well end up being a "you live in a different bubble than I do" which I'm not about to argue or criticize. I just wanted to chime in from a music-nerd-often-accused-of-being-hipster's perspective; if only to speak for my friend group and myself, we find these terms to have inoffensive utility.