DTM can be useful to those that are recovering from an injury (once the client/patient is out of the acute phase), for athletes, for people with postural strains, or people with chronic pain. Typically there is an area or a few areas where this type of work is needed. For example, a person who has chronic postural pain/tightness from sitting at a computer, might need DTM to their shoulders, chest, and upper back/neck. They likely, do not need DTM on their whole body. Some therapists might disagree with me here, but I rarely think a full-body, DTM, is needed. It can simply be too much. I would rather see a client more often, for less-intense sessions. It is simply more effective. It is the same as Physical Therapy- it is more effective to do it regularly.
Couples massage is a good choice when lovers are in the throes of early romance, and can't bear to be apart. They want to share everything, even their massage. Many couples treatments are specifically designed with romance in mind, including time alone in a rose-petal-strewn tub, a bottle of Champagne with strawberries and chocolate, and lounging time by a fire after the treatment. Part of what you are paying for is a time in the room, which works best when it's a beautiful romantic setting.