At least Worf had a regulation uniform with his sash. Although I thought that was sort of stupid too.
Same thing, if you are supposed to wear a uniform, it supposed to be uniform.
They had her dress that way to be eye candy. Plain and simple.
I agree, I think eye candy is a big part of her outfits. I still think her black outfit with belt and bun was okay though, as it made her stand out and wasn't as tight from what I remember.
Worf's sash doesn't make any sense either , but I think it worked for what the the producers were trying to convey, just like I think Troi's outfits worked for the most part.* Mostly eye candy because Marina Sirtis is beautiful and only added to that. But I think it also conveyed that she's exotic, supposedly more sensitive, consoling, etc. When Picard and her have those one-on-ones, it seems more plausible that he might be more open to someone in casual attire, as opposed to confiding to an officer in extremely formal officer-wear. Just like Worf comes from a warrior culture, and him having the sash helps reinforce that idea for the viewer. Notice it wasn't all the women, just Troi.
*No, the onesies kind of get on my nerves too. It's not necessarily because it's form fitting, or because it gives her character some sex appeal. When she's walking in some of those scenes, it's like she's a big kid, Alexander's playmate. And considering she's already busty, they didn't need to show cleavage.
One more thing. Why would an empath wear deliberately revealing clothing as a ship's counselor? I mean, she can wear what she wants, but considering that it benefits her to make her patients comfortable and at ease, I don't think that being beautiful AND wearing tight revealing clothing would help them. If I were Barclay I would be extremely nervous and embarrassed that she would know that I'm aroused or attracted to her.
I like Ilia's look for TMP, for its time. But wow, she's pretty much just wearing an extremely short bathrobe. Maybe that's her culture, and the bald head helps to desexualize her somewhat. Slightly. But it's another example of "c'mon! we see what you're doing producers."