Of course, there could be another reason Tonia Barrows never got to come back: she's the only crewmember besides Kirk who got to wander around with a ripped uniform.
When Barrows was walking around the Shore Leave planet "thinking all a girl needs is Don Juan," the machinery figured she wanted a sex-bot, and built one. Same with Kirk thinking of Ruth.
At the end of the episode, if you check out their smiles when they enter the bridge, it's easy to infer that they indulged after the Caretaker brought them up to speed. Whether Barrows took up with Don Juan or McCoy, she and the men obviously had an adult vacation.
I think it's more fun the way TOS did it versus TNG. With Kirk and company, the viewer can decide how steamy things got. But when Picard or Tasha Yar went to a pleasure planet, I always felt like we were getting a little too much information.