"You better watch that girl. […] To see she don't get you to marry her," Call said. "You're just enough of an old food to do it. I won't have that girl around." (2.75, 2.77)
Some men in Lonesome Dove look at marriage as if it's a sort of trap. Call is one of those men, maybe because he views love itself, or any human connection, as less like a bond and more like a ball and chain.
Little marriages were what they wanted—just something that would last until they started up the trail. Some girls did it that way—hitched up with one cowboy for a month or six weeks and got presents and played at being respectable. (3.45)
With such a high divorce rate today, it's easy to think of modern-day marriages as "little marriages." But Lonesome Dove shows us that marriage has always been a temporary situation to some people. 'Til death do us part? Not so much.
[July] had arrested plenty of people who misbehaved, yet he could not bring himself to say a word to his wife about her own unusual behavior. (27.11)
It seems like marriage problems aren't to be talked about in the world of Lonesome Dove. It's a fake-it-'til-you-make-it situation, where July feels he is expected to just act like everything is fine. But is a fake marriage really a marriage at all?
"How would you know?" [Elmira] asked. "You ain't been married to him." (53.24)
It's easy to hate Elmira, but she makes a good point here. As we later learn from Clara, being around July Johnson for too long sets you up for a mind-numbing existence. We might leave him, too, in Elmira's position.
"You git," the old man said. "Don't be talking to my wife." (68.46)
There's a recurring motif in the novel of creepy old men being married to really young women. One is Janey, who is resourceful enough to run away, but this old man, encountered by Jake Spoon, seems just as mean, treating his wife as property and determined to keep her to himself.
"I couldn't sit around in a house all day," [Jennie] said. "If someone was ever to marry me I expect I'd run off too." (69.109)
In Lonesome Dove, marriage means settling down. Maybe that's what it always means, but it's especially apparent here, where cowboys and whores live roaming, nomadic lifestyles.
The idea had shocked Bob, a conventional man if there ever was one. He could not believe he had married a woman who wanted to live like an Indian. He worked hard to give her a respectable life, and yet […] she stubbornly kept her own money; year after year—for the children's education, she said. (75.33)
Bob believes in traditional marriage roles, and while that may have seemed nice for him, it's a good thing Clara never really bought in to it. After Bob's accident, where would Clara be if she hadn't kept her own money against her husband's wishes? She wouldn't be able to take care of him, that's for sure.
"What's the matter with you, Zwey?" Luke said. "You and Ellie aren't really married. You ain't married to somebody just because she comes on a trip with you." (76.15)
Some men just fundamentally misunderstand marriage, and Big Zwey is one of them. It's easy to laugh at him, but how is he supposed to find these things out if no one tells him about them? Marriage is an institution created and developed by people; it's not just something you do by instinct alone.
The principal aspect he worried over most was that marriage required men and women to live together. He had tried many times to envision how it would be to be alone at night under the same roof with a woman—or to have one there at breakfast and supper. What kind of talk would a woman expect? And what kind of behavior? (12.63)
Living on the range is a lonesome existence—that's a recurring theme throughout the novel—and cohabitation after a long time alone can be scary. No wonder so many marriages between cowboys and women fail. They don't know how to act with one another.
"No, ma'am," Roscoe said. "I was never even engaged."
"In other words you've went to waste," Louisa said. (37.63—37.64)
There's a bit of a role reversal going on here. Generally, an unmarried woman is viewed as a spinster, or a waste, but here Louisa accuses Roscoe of going to "waste" for never being married. Maybe she realizes he's not good for much else, anyway.