If society marks you and your behaviors as deviant, you will be rejected in some form or another. Whatever isn't useful to the reproduction process is labeled undesirable until the moment when it becomes useful; that's understood quite well. So, if the goal is to normalize and expand the realm of inclusiveness, would that not entail such subcultures, identities, and such become useful for capital?
I've been to spaces in the underground many times, usually anarchist ones, usually ones created in the moment of all spontaneity. People play by their own rules. They do not answer to anyone except those with whom they share their space. It's the feeling of autonomy that comes. We have no need to ask for permission from above but only need to understand ourselves from below.
The beauty may very well be in the obscurity. When I've encountered people who speak of assimilation, they spoke of their fears of being forced into the dominant culture on the basis that it robs them of some kind of unique specialness found within the identities they've crafted for themselves. Their reasons for preserving the obscurity are only for superficial reasons. It is not the chains of bourgeois culture they are resisting, but - like an angst-ridden high school teen - their fear of becoming like "everyone else". They want an image of themselves that they can exploit for greater social capital from others who see their identities as something worthy of praise, regardless as to whether or not those individuals in question have any real substance. This attitude, of course, eventually becomes tangled up in the society of objects; when those from the dominant culture are chastised for appropriating or imitating the relics or rituals of the outsiders it is because the specialness of the object carries over to its clique.
Even though we can agree that appropriation has negative consequences and obviously relates to ideological domination, the liberal perspective does not understand a much greater problem caused by assimilation and what it means in terms of loss. Hegemony by the ruling class extends far beyond the pilfering of little possessions and artifacts. What is truly lost in the possess is the knowledge gained from the experience of having been on the margins of society, the understanding of everyday life that can only be obtained by seeing it from the bottom.
Years ago, back when Occupy Wall Street was a thing, there was an older man with whom I spoke at Zuccotti Park. He told myself and the little group around me that he had been an anarchist for over 40 years, and within that time he never held a real job, nor did he complete school, nor did he own basic technology like a cell phone or television, much less a house. The justification he gave for promoting his absurd lifestyle politic was that he could only feel the need to rebel against capitalism and the state if he stood in contrast to it. This man was very well-read and spoke like it, but book knowledge wasn't nearly enough. He chose to remain at the bottom so he would keep the wisdom that he had gained from his insights, and which he willingly passed down to us.
Assimilation equates to forgetting. Those within the mainstream have the ability to be shielded from these realities. It's as if bourgeois society makes everyone wear a pair of cloudy glasses where everything that would be seen or remembered becomes very hazy. We all know that social hierarchies exist (who hasn't seen a plethora of internet posts talking about "privilege"?), but their implications are very distant from us. Perhaps its the case that the people making those kinds of statements are themselves very removed from those experiences; we're often told that those who fight for social justice only do so because they have "nothing else to worry about". It's a sign that they've lost their connection to the struggles of the past, because they have no knowledge of these things. That's a lot more important than a preoccupation with consumerist forms of "I want to be special".