They put her in that costume to try and make her hotter.
(1)this demonstrates that they had no understanding of what an attractive woman should look like as she'd have been much more attractive in a starfleet uniform with her hair down than a tin foil catsuit and headmistress' hairstyle.
they succeeded in making her look frumpy and about 10 years older
They did the same thing with T'Pol on ENT and pretty much the same thing with Deanna Troi on TNG for a few seasons.
I think all the catsuits spanning these series illustrated (1)
And yet her character was probably the most recognizable thing Voyager had going for it in mainstream pop culture during the time it aired, and we're talking about her outfits and how yummy she looked a decade later, so I think they knew something
about what people liked to look at.
You can't please all the nerds all the time, but someone
liked the cat suits.