I'm not "Jeff's" marriage counselor, nor exposed to all the private details of his or any of my other friend's lives. It could just be that birds of a feather flock together, and we're all generally friends because we share similar personalities and weaknesses and that just leads to a high correlation of similar relationship strengths and weaknesses.
If you can't ask your partner for intimacy, then it's not biology, it's communication.
You can ask for sex, but I don't think you can ask for intimacy -- intimacy requires an organic desire that originates within the partners. Sex can kindle intimacy, but it can't create it.
I think one of the challenges, though, of the asking is that if you ask and you get it, what are you actually getting? Are you getting a partner who is motivated out of an organic, genuine interest, or are you getting a partner who's going along to get along?
At best you might get a partner who provides a theatrically convincing orifice for you to orgasm in. At worst, you get an emotionally dead, passive participant, the stereotypical cold fish who just lies there and might as well have a visible thought bubble that says "Are you finished yet?"
When people complain about "not enough sex" I suspect that it's not exclusively frequency that's the complaint, it's at least as much a complaint about a lack of organic, internally originated enthusiasm for sex.
I think some men just don't care (the old joke: "Why do women fake their orgasms? Because they think men care."), and view sex as the same whether she just holds still long enough for him to finish or whether she puts on a garter and fishnet stockings and talks dirty. It wouldn't surprise me that lack of sexual satisfaction among married men today is a function of women who don't feel obligated to go along with "the marital duty" and men being more aware of what their wives actually want, creating a kind of negative feedback loop.