I think it's understandably often more comfortable to be in the 'norm' of society. To feel like somehow one doesn't need to singled out for their traits. So for those who say it's uncomfortable to be identified through a specific label like cisgender... I get it. But here's the thing. Just because it's uncomfortable does not mean the term is inherently damaging or insulting. The comfort of fitting with the historical norms of society seems to partially come from feeling like you are the default to which anyone different is an outsider, but those who don't fit those norms don't deserve to feel some far greater discomfort simply because of that.
There's absolutely no reason to consider individuals who are not trans as "just men and women", that's both immensely insulting because of the contrast it draws to trans people and it honestly just makes any discussion about trans issues so needlessly muddled when more concrete terminology can make things clearer. Having a term for people who aren't trans is incredibly useful for these discussions and it also allows a sort of "leveling the playing field" by not assuming through language that one of these two groups is "normal".
And for those saying "I just want to call everyone a person, I don't need to use the terms transgender or cisgender" I think your heart is very likely in the right place but the fact is in modern society the world and society still makes it so that the experience of trans people has many different elements to it than cis people. While I can't speak to the identity of a trans person, as a gay man I actually kind of dislike when people tell me "oh well I see you just the same as everyone! To me you're not a gay man, you're a man." But I am gay. I've gone through a lot of experiences and personal struggles because of that part of me and it's shaped my identity in a way I don't want simply stripped from me. In just the same way I think it's important to recognize the unique identities for those who are trans, those who are black, etc. These identities matter, both from a point of examining large issues still very present to this day, but also because these labels do reflect differences in experience that could very well matter to people.
And when we take the time to recognize these identities and the experiences and struggles unique to them, I think a small but very important part of that is to be sure that, when speaking about trans topics, other queer topics, racial topics, and more, we don't simply assume that the majority group goes unlabeled simply because some feel they're "normal".