Why do you think? We evolved gender roles for survival reasons. Nothing is wasted. Gender roles are psychologically embedded within us. Even those who pride themselves for not caring about such things and being above such stuff often falter when you look a little deeper into their psychology.
Something I have learned about myself these past several years. Growing up gender roles did not really make much sense too me, yet digging a little deeper I can find them there. Albeit in my case I think genetic mutations make me express gender roles in a somewhat skewed manner. I used to look down on conservative and feminist men, and while I have been willing to treat women like dirt just as men, there are times where my white knighthood becomes really sappy. Even if my expressions are somewhat different, I am not immune and above such things.
There is also good reason for there being more historical pushback against men acting like women than the other way around. Men evolved a psychology to be more expendable for a reason. Mainly sperm is cheaper than eggs. Losing a few men is not the same deal to a population as losing women are. One man can impregnate multiple women. It makes perfect sense that we evolved socially to be more protective over women's physical well being more than men. Hence the reason women are more neotenous than men on average. Evolution works as increments. The easiest path for women to be perceived more worthy of protection is them piggybacking physical cues such as cuteness and smallness that we have already evolved for being protective over children.
When a man takes on more feminine roles and mannerisms other people take this as him broadcasting that he may not fulfill his role as a man to potentially lay down his life for a woman, and even worse expect to be treated as a woman and given the same protection and safety that isn't given to a man. This can send many people men and women into a frenzy.
There are of course interesting exceptions to the rule. Human psychology is complex. Men of higher status are naturally given more protection and care than men of lower status. People in the past have pointed out men in centuries past wore makeup and more elaborate colorful clothes as proof that gender roles are social constructs that change in time. Yet I am not so sure about that. The higher classes did, yet the more common man had more a of a rugged appearance. I think when you see instances of men acting more feminine and not being punished for it, it is still within our biology. Those men are of importance so the idea of them giving out more cues of protection is understandable. All men might have a switch where under certain social circumstances they act more feminine. Still.. at the end of the day I see a biological competent. Something that doesn't threaten the women "child" man "parent" evolved psychology view.