Some other already gave good possible explanations to this, but I am adding my own subjective uninformed view on this:
Not many people may actually like wearing crop tops but they do it for ‘fashion’ reasons and those fashion reasons so far dictated that women are the ones who have to wear them.
Me, as a man, haven’t personally tried crop tops, but it feels to me like it would be uncomfortable. It feels actually uncomfortable to me when sometimes I wear an old t-shirt at home which has become shorter leaving some small lower parts of my back or abdomen uncovered. And it’s not because of any social construct, I live alone and nobody can really care about what I wear, so it’s not that. But it’s like feeling cold on the lower back of my torso but warm in the upper part. It just feels uncomfortable.
That’s just my personal feeling but I can imagine more people could feel the same.
So I can imagine wearing a crop top can give a similar uncomfortable feeling?
But sexualization of women required them to expose more parts of their body (most of their torso) while covering those ones not considered to be decent enough to be shown in public (breasts). But that sexualization and exposure of their bodies is something that is usually not so much required from men.
I think the original question asks why not so many mean wear crop tops as a choice they make, but I think it hasn’t been so much a choice for women as it may have been a command from sexualizing fashion and the heteropatriarchy has determined that the uncomfortably and exposure of their bodies related to crop tops is something women have to wear not always because it’s their choice but to comply with sexualized fashion standards.
I am not a woman or wear crop tops either, so I may be wrong on all this, I’m mostly just thinking out loud 😄
LGBTQ+ and labour laws are very different across countries, so it’s very difficult to talk generally about how this works without being specific to some country.
I will talk about Spain because there’s where I am from and where I worked most of the time.
You generally just cannot fire someone for arbitrary reasons before their contract comes to an end. You really have to justify why you need to fire that person, like having several poor performance reviews against them. Otherwise, you may risk having your firing judged as “unjustified” and having to pay that person a big compensation or even the firing being judged as void and having to readmit them to the position you fired them from.
No matter whether they are cis, gay, straight, man, woman, POC or whatever, you just cannot fire someone without a valid reason unless their contract has come to an end and you don’t renew it, that’s basically it.
So could someone argue that your sexual orientation or gender identity is a valid reason to fire you because being gay doesn’t fit within their company culture or having trans people may cause them an image problem?
No, article 4.2.c of the Worker’s Statute says you cannot be discrimanted for employment based on sexual orientation or gender identity, among other criteria like ethnicity, age, union membership, etc.
So you couldn’t be fired for being either gay or straight, man or woman, cis or trans, etc. Nothing of that is a valid reason to be fired.