It isn't the fact that he hit on her clumsily the first time they met that makes her continue to deny Cadet Kirk her first name. Or the fact that he accidentally felt her up less than five minutes later in the middle of a brawl in her honor-- and had the gall to grin drunkenly at her as he did so. It isn't even the way he stalks her intermittently around the Starfleet Academy campus for the next several months, joining her clubs and chatting up her roommate and turning every non-linguistics class they share into a battleground.
The thing is, Uhura has met boys like Jim Kirk before, and she knows that he's more or less still a puppy at heart: too energetic for his own good, not sure yet where to put all his limbs, only half-trained in the social niceties, and without a genuinely malicious bone in his body. If they'd got to know each other somewhere before Starfleet, they might have been on a first name basis right away-- at least, once she'd whacked him on the nose with a PADD to make sure he knew which liberties she wouldn't tolerate him taking.
But they are in Starfleet. An organization that pretends to be egalitarian-- where anyone who passes the entry exams, swears the oath and completes the training, no matter their origins or beliefs or preferences, can rise to the top ranks-- but which still relegates women mostly to support positions. Where the only female Captain she knows who earned that rank at the helm of a starship is Captain Pike's former first officer-- and it was as much his recommendation as her record that won Number One that position. Don't even get her started on the disproportionately preferential treatment given to native Standard speakers; she's one of only a handful of cadets attending the main 'Fleet campus from the United States of Africa.
Uhura will not tolerate anything that reduces her to just another female cog in the machine. And every time Kirk turns that mischievous blue gaze on her and comments loudly on her 'talented tongue', she can see her IQ drop twenty points in the eyes of most of the cadets around them.
Half the time, of course, he only takes her non-responses as a challenge, but she's not going to waste her energy trying to explain it to him more clearly than she already has. She doesn't care about the sob story lurking in his past about a long-dead father and an emotionally absent mother-- it's still not her job to educate him about the offensiveness of his unthinking privilege.
Besides, given his contrarian nature, that might just make him worse. Uhura tries to imagine him cheerfully deciding to fix 'Fleet's gender role inequities by indulging in ever increasing levels of 'equal opportunity' flirting-- worse than he already does, anyway-- and rolls her eyes at the thought.
He isn't alone in his objectifying behavior, of course. But he's the most egregious example she sees on a regular basis, and shutting down his every attempt to befriend her helps reinforce her determination to succeed. She can't fight something as vague as 'the patriarchy'-- but she can defy the bad example Kirk unwittingly represents.
Maybe one day he'll grow up. Maybe one day he'll find something worth taking seriously, realize the way he treats female officers matters, and settle into an officer worth serving. On that day, she will deign to allow him first name rights at last. But until then, all the puppy-dog eyes in the world won't convince her to let him encroach one inch further into her personal space than he has already.
Or remold it. If she lets the lingering gaze of male cadets bar her from skirts, or long hair, or flashy earrings, that would be just another kind of giving in. She enjoys being a woman, as she thinks that fascinating Vulcan professor in the computer science department has finally noticed-- which is all the more reason for her to draw this line, in a firm and unyielding hand.
Her name is Nyota, and she refuses to let anyone make her feel inferior without her consent.