While Troi's uniform pre-Jelico may have been for titillation more than anything else, in the show it DOES make a degree of sense.
She's a counselor, her primary job is to sit with people and talk about things in a relaxing, comfortable, environment. How at easy is someone going to be sitting there talking to a woman in uniform holding a higher rank than you? It might provide an ounce of pressure on someone that could make a counseling session difficult.
Getting the ACTRESS in a "normal uniform" was a good thing, sure, as it no longer diminished her character and used her simply as eye candy. (Which, really, compared to T'Pol and Seven, Troi was the best of the eye-candy women in the modern-Trek series in how she was treated on the show.) But it could certainly be argued if getting TROI into a regular uniform made sense in-universe when you consider what her job really was.