I agree with the "young, single mom gets poor care" approach (that it happens, that is, not that it's a good thing).
I have a friend whose first birth was as a teen mom - induced, but without pain medication at any point and of any kind. It was a fast labor (her then-boyfriend was with her for the labor, she never took a birth class).
Her second baby was a longer labor, with a husband who'd never been at a labor before. She wanted a natural birth, they did classes, and he was just overwhelmed with how much it seemed to hurt her. She opted for the epidural because, she said, he was so worried about how much pain she was in. She ended up with numbness in her legs for several weeks, headaches, etc. If they have another, I think the plan is to have a doula there too and kick the anaesthesiologist out of the room. .
It's not that her husband wished her malice, he was overwhelmed by her pain and wanted to fix things. I think it's a combo of men thinking that they should 'fix' things (and not wanting to feel guilty about 'causing' this pain), and women wanting to please others (especially a panicked spouse). Plus, we trust them. If they think it's that awful, and we feel that awful, then we must need medicine. The fear of birth we have as a culture plays into this, because men and women are both afraid that birth is earthshatteringly painful and catastrophic - that's what they see in the movies, on TV, talked about among friends....
I've another friend who told me that if she ever gets pregnant, she doesn't want her husband in the delivery room at all - she doesn't want him to see her "like that."
When we were teens, we found the love letters my Dad had written my Mom while they were engaged. He wrote about worrying about how much pain she'd be in when they had babies. Mom had all 7 births with no pain medications at all, Dad was one of the first dads allowed into the delivery room at that hospital. He fainted during the first birth (not surprising, the doctor cut a horizontal episiotomy on Mom).
I think the real factor, then, is a combination of how strong the woman's knowledge and goals are - and how willing her spouse is to educate himself and support her in labor. Dad didn't go into it confident; but he became confident in Mom's capabilities over time. Likewise - my uncle has said more than once that he'd LOVE to be a doula. He and his wife had five babies, all natural births, and he loves birth. He's in awe of what women can do (the best part of this is, he's a crusty old rancher, totally incongruous I suppose).
My husband went to birth class with me, and I read passages aloud to him while I was preparing. Went over the plans, and told him, "Don't suggest drugs, and if I ask for them, tell me NO, because I don't really want them." He was kind of on autopilot for our first birth -- scared. He told me, he was so afraid that something awful would happen to me and the baby that he just couldn't really think. Seeing his first birth calmed him down - he was very competent for our second birth. The advantages I had with our first birth were that every woman in my family has had natural births, so I was confident - and we birth quickly, so there wasn't time for the hospital to intervene and muck things up.