Clearly, as Thomas Maier shows, that was the case in the marriage of William Masters and Virginia Johnson. It's not just that a quasi-forcible sexual relationship devolved into a quasi-loveless marriage. It's that Gini Johnson, for all her sexuality, never thought of looking outside the marriage, apparently. It's that Bill Masters apparently, until his end-of-life marriage to a college flame, couldn't be with a woman unless he could dominate her.
In a sense, they both, despite their groundbreaking research on sexuality, come off as old-fashioned, not on morals, but on personal psychology. With Masters, I think that "informed" some of his unscientific work on homosexuality. With Johnson, I think it was behind her refusal to get involved with feminism.
Anyway, if you don't want to accept just my judgment for this, Maier presents a full dual biography of both sex researchers, back to their childhoods, and what from that may have made them tick the way they did as adults.
And, a sidebar about the "love" in the subtitle. Masters and Johnson, while encouraging Americans to be more comfortable about their sexuality, only taught Americans indirectly how to love. They may have taught them how to "make love," but that's different.
That said, the author says the subtitle was his idea, and intended to be ironic, in part. Maier also said, though, that he thought the two were in love, bittersweet as that match might have been.
And, you can see that in Maier's book, too.