Maybe this is just a European thing, but something I notice if I ever watch documentary or interview-style TV from the 70s/80s/90s is how common it used to be for men with receding hairlines to grow their hair long.
It's not the only thing that's changed since then, ofc. There are so many ways in which what you might call "cosmetic non-conformity" has become much less common, but the reason the receding+long hair style is one that stands out so much to me is that I think it is related to gender in a way that's quite interesting.
There's a popular British comedian called Bill Bailey whose distinctive signature look for decades had been a bald crown with long hair brushed back (a look he called "the skullet"). A few years ago, though, he shaved it all off. The general reaction from the British public was, as usual in these situations, "Wow, he looks so much better!" but I couldn't help feeling a sense of loss when this happened, that I didn't really understand.
On reflection, I think the receding+long hair look is clearly a kind of gender non-conformity. Long hair in men is already somewhat GNC here, because hair length is one of the many attributes that contribute to perceived sex-gender in this particular culture. But receding+long hair is a style that incorporates features that are read as both very masculine and feminine simultaneously, and I think the instinctive revulsion people feel at seeing it comes from the same place that a lot of transmisogynistic revulsion also comes from.
There's something about how sufficient exposure to Testosterone closes off certain avenues of socially acceptable self-expression that makes me feel incredibly sad. The idea that it's particularly embarrassing for a man who has been hormonally masculinised (perhaps against his will) to attempt to appear in a manner that is read as feminine is pretty much a textbook example of the intersection of traditional and oppositional sexism, even if not necessarily transmisogyny.
Long hair in those perceived as boys is often a marker of the transmisogynised in itself: I'm thinking of the image of the sad, softly-spoken, long-haired uncracked egg, or the fairly common transfeminine experience of being forced to have your hair cut against your will. Long hair can be a small act of gender expression, even a shield, against a world that refuses to let you express yourself otherwise.
But then the idea that this form of self-expression is time-limited, that there will come a time when Nature takes away that shield and forces you to embrace manhood, and even if you persist in using that shield by wearing your hair long, the social cost of doing so gets higher and higher until finally you break and cut it off, and a group of men gathers round you to say "see, don't you feel so much better now?" That feels like such a clear example of gender being policed, and gender conformity being rewarded, that it kind-of shocks me how uncritically it is accepted as just normal, even in progressive circles.
There's a Youtuber I follow who has always given me eggy vibes. His hairline has been receding for years, and he has been increasingly getting comments saying "Shave your hair bro, it looks ridiculous". He recently did just that, and the comments have shifted to "You look so good now!"
From a purely aesthetic PoV, I don't even agree: I think the receding+long hair look is often really cool and I love seeing it on the rare occasions that I do. But also I felt an inexpressible sense of sadness in realising that these complimentary comments have an undertone of "I doubted your commitment to manhood before, but you've seen the light and definitively joined us, well done" that I find sinister and unsettling.