Because that's a cop out and devalues one of the most important female figures in comics
Lois Lane and Superman were created as a pair 76 years ago. Lois is one of the only female characters in comics history literally created from issue #1 to be a foil and potential partner. While other love interests across the landscape were additions or afterthoughts, this is a rare woman character who legitimately was part of the design and landscape of Superman from the ground up.
There is a lot of sexism that surrounds trying to get Lois out of the way as the love interest. A lot. She's not a typical sexy girl in a sexy male gaze costume (though she's obviously very attractive) and that's part of it. She's also been subjected to decades of crap in an industry that hasn't always done right by women and yet she's endured.
The bottom line is that Superman's love for Lois Lane--- for a human committed to finding the truth---for a human who reached out her hand and wasn't afraid of him when she had every right to be---is a building block of this story and it's a role that she's earned.
There is a very bad habit in culture (bc it's often told from male POV) to treat love interests as interchangeable and to assume that men have to play the field. So here we have a superhero who, consistently, for 76 years has come back again and again to the same woman. He's been married to her multiple times. She has transcended what we, as women, are usually told ANC usually get in these stories. She's become a hero in her own right and a great example of the way in which women devoted to their jobs can also be worthy of great love as opposed to the cold, sexless "you have to choose between career and family" message that women have been getting repeatedly for decades and is still very real.
The most powerful man in the world breaks all stereotypes about what women "should" be and falls in love with an aggressive career woman who doesn't wear a sexy outfit or pout for the camera. And she doesn't always say the right thing. But she tries really hard. And that's amazing. It's amazing. And yet...you get these men who just can't wait to kill her off or push her aside or carefully (bc hey even they know that fridging is wrong) replace her with someone else. And then you wonder why there are women here who need to excuse themselves from the thread bc they can't handle the disgust.
Lois Lane is in the DNA of Superman. Lois Lane and Superman's love for each other---the messy, human, perfectly imperfect---love they have for each other is in the DNA of Superman. It's one of the :
nly:: male driven hero properties to have that kind of consistent driving force. Devaluing it or assuming it's something easily replaced is problematic as hell. And it Pisses. Me. Off.
(P.S. Kingdom Come is set in a reality where Lois and Clark were married for YEARS and the only reason Superman winds up with WW is bc his wife is dead. Mark Waid has spoken at length about his feelings on this. He has clarified repeatedly that the story was a "cautionary tale" and not a "how to" guide. He's also clarified that KC still upholds that Lois was the love of Superman's life. He's also commented that he's not sure in retrospect that he doesn't think the SM/WW works "long term." KC is a very specific story that worked only under very specific circumstances---the murder of Superman's true love. Which is a tired plot and not one I need to see for yet another woman.
As for the new 52? Let's put aside how ragingly disrespectful the entire thing is to the legacy of WW who was created with her own supporting cast and love interests that no one ever ::sees:: bc DC is so sexist. The reason that Superman turned to WW in the new 52 was bc he didn't feel he could burden Lois with his secret. He wanted her. He loved her. He pushed her away bc he feared burdening her. It was a stupid,forced roadblock designed only to get Lois out of the way undercut by decades of narratives proving that Lois has the right to decide for herself her own life choices. However, given that Lois already knows that Clark and Superman are one and the same in the Man of Steel universe and has already had the opportunity to prove that she accepts him completely, this forced reason has no relevance to this film franchise. If falls apart.
You know what would be new and novel? If, for once, a relationship could be allowed to progress and last without being subjected to this crap. What if the woman who appeared in Action #1 beside Superman and the love story that started it all in comics was treated with the dignity it deserved and preserved and respected? Bc that? Would make me respect this director and this franchise. Lois Lane has earned that much. :: They:: have earned it.
made an interesting point about women being killed off in such movies. I never thought of that at all. What if this Lois functioned dually as Lana in a way? By that, knowing his secret and being the closest friend even if their relationship was too complicated to work out. I'm thinking they will stick to Lois and Clark as a couple by the end of the series, but Snyder may toy with a triangle or two at some point. 
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In more ways than one 
