This trend is most prominent in fantasy books, I've found, as those are the types of books where the main character is plunging herself into immediate danger. So, let's set the scene: the mystical woman with her magic powers has to defeat the other mystical woman who has magical powers who only slightly differs from her because she's evil. Right. So then enters "Love Interest." He's tall, handsome, manly, and probably has abs. (He also probably doesn't own a shirt if it's the same-old stupid fantasy book that's ever been written.) Well, she tell him of this quest she has to go on and he says he's coming with her to protect her. This is the first sign of overprotective love interests.
Well they go plodding along in search of the destination for this quest. He is kind, understanding, and helpful, even. He will follow the heroine wherever she goes. They run from the same enemy together and devise plans on how to trick the enemy together.
Then something happens to "Love Interest"'s mind. The heroine told him so many months ago "I am a powerful magical being that is the last of her kind and I must go and defeat my enemy. I have deep power within myself even though I am incapable of doing absolutely anything. I am no match against my enemy even though we all know I'm going to viciously kill her in the end. Surprise. Surprise." and it's just now penetrating the inner membranes of his cranium. He just now realizes that his heroine is putting herself in direct danger and now he's not going to let her do anything but be a helpless and brainless woman while he plays "man" and protects her.
She get's mad at him, as any woman who had incomprehensible power might do. She disobeys his commands to get below, behind, and out of sight, and goes above and beyond in the call of duty. She shows that she is capable of fighting the enemy better than he ever could with his mundane tools. He get's mad at her because she is a sensible woman who doesn't need a man to rule her life. He insists that he needs to protect her by risking her life instead of hers. Apparently he thinks this is a valid argument because he's a man and she's just a stupid incapable and frail woman, despite the cosmic powers she's already displayed to him millions of times.
She is still attracted to her so called "Love Interest" even though she's made herself into the stupid woman he thinks she is by arguing with him and pounding at his chest in anger oh-so-heroically. Eventually they have a fallout and he pulls up the point of "can't you see what you're doing to me?" blah blah blah. She consents that he's right even though he's being selfish by telling her she can't fight for herself if she's going to get killed when he's going to put himself into danger just as much as she would. She turns into a stupid and dainty woman and let's him think he's the only person that can do anything because he's the man.
You know what? I would've dumped him months ago. He needs to realize that their situation warrants danger on both of their parts and that she is just as capable at defending herself. She's not a useless woman and he shouldn't treat her like one. She can fight just as well as he can and she can help too. He shouldn't be thinking that she's stupid. I think if they get married he's going to treat her like property and so help me if I have the love interest rescue my women in a book, let a million pounds of books fall atop my head for my stupidity. He's such a baby when she tries to put him out of the way of danger, and he resents her, but she's expected to just go along with whatever he says? No. I don't think so!
Yeah, well, I was reading this book and I was getting really fed up with the characters. If you couldn't tell.