Do you have a nickname or a preferred name? I do and Im a cis man. My nickname is a less common nickname of my full name. If you call me by the more common nickname I usually do not respond because in 50 years that was always a different person's name and not mine.

If you know me for long enough and you keep calling me the wrong name I am going to think you are pretty rude because you should know my name if you know me.

It's the same way with pronouns. No rational person is going to jump down your throat for using the wrong pronoun the first time as you aren't aware of their preference, but when you have been told a few times it is rude.

I'm going to assume you're a cis man for this.

Let's say we work together. I insist that I don't care about gender and see no reason why I should. As such, I decide to refer to you as 'lady' or 'girl' over the course of our daily conversations.

Would that not bother you? You don't think that wouldn't eventually start having an effect on you? Being constantly misidentified, misgendered, or having a part of who you are be literally disregarded?