I like to think it's in keeping with Itami's character. It's easy to forget because of the harem, but to the rest of the world he's a complete screw-up who doesn't have the respect of his men or his fellow officers, and every time he takes action he does it in the most passive way possible. He has no drive and no ambition, so of course he's never going to realize how great his romantic situation actually is or take advantage of it.
Contrast with the smartass LT, who earned his position through hard work and talent. He may not have been lucky enough to be in the right place at the right time to be labeled a hero like Itami was, but he's actually good at his job and knows how to play workplace politics, so he's going to end up with a better career and a more complete romantic relationship with his hot bunny girl.