To better understand the relationship between tantra and therapy, it helps to understand a little more about sexual arousal. Early sex research in the 60s and 70s focused primarily on lab studies, which naturally required recruiting individuals and couples who were able and willing to have orgasms in extremely clinical settings while wired up to machines and being observed by other people.
Needless to say, the research subjects weren't representative of the larger population. In particular, they typically did not include people who had low libido or had other problems getting aroused. This led to models of sexual response that were either vague about the questions of desire and arousal, or which made definite statements about desire and arousal that turned out to be wrong for large parts of the general population.