Yes, because the general idea behind the sexy attribute is attracted people will try to court the sexy person and give preferrential treatment. They become blinded by lust and are affected by the attribute's benefits. If you're already in a relationship, it's likely you won't try to court someone else, so you're not affected nearly as much as someone not in a relationship.
Now, for your other points against love in the RP:
Two men are prisoners of war and are tortured for hours on end. Both are told that the torture will never stop until they are dead or give all their intel. One has nobody back home who loves him or will truly miss him. The other has a loving wife and other family members back home.
Soldier one has no reasonn to live except for the sake of living, and nobody back home he cares about who his intel would put in jeopardy. He'll likely spill the beans or lose the will to live and die in his seat.
Soldier two knows his inntel could cost them the war and put his loved ones in jeopardy. He's more likely to keep his intel and either die at the hands of his torturers, or be rescued.
So you can see that in such instances having a lover is beneficial.