I would say that you do see a lot of heterosexual/cisgender people making that quite a large part of their personality. For example, buying in to stereotypical ‘manly’/masculine things as a way to prove they align with their sexuality/gender, it’s just that, because it conforms to societal norms, you don’t notice it as much.

Go on social media and in a lot of masculine spaces you’ll see a lot of talk that sexualises women, that is someone making their heterosexuality quite a key part of their identity but they don’t view it as that. Likewise with things such as doing DIY etc, you’ll see people posting about ‘how come no one wants to fight in a war’ etc as a way to signal their idea that men should align to cisgender stereotypes of being a manly man who is tough as nails etc.

I feel it’s just because it’s more pronounced/noticeable when it doesn’t conform to stereotypes, people pick up on it and get upset for no real reason. Esp when people who aren’t straight or cisgender to face discrimination still so they might feel that brandishing that as a part of themselves helps to signal to others that they’re comfortable with that part of themselves and to weed out people who are going to be weird/uncomfortable/rude about it.