Why were Tara and Willow wearing un-fashionable clothes, such as stupid princess dresses and long skirts as buffy wore the BEST clothing?

Well, technically this isn't a सवाल for here as it's a matter of opinion that they had bad fashion sense, not a fact about the show.

If आप want a reason they didn't dress like Buffy, who was और into fashion it was because the wardrobe department did their jobs properly. It wouldn't have made sense for their characters to dress the same as Buffy since Buffy was the only one to have ever shown an interest in fashion. Willow and Tara were not into fashion and were slightly geeky characters so they were dressed in a way that fit their characters. It would have been dumb and unrealistic to have the geeky witches dressed in the same style as the character who liked fashion.

Like I कहा though, that doesn't mean the looked bad या stupid, they simply had a different style than Buffy.

this a सवाल about opinion. Personally i think it is because of their individuality as a couple. I know they didnt have the best taste in clothing but it comes to दिखाना that its not what आप wear on the outside that counts.

From the start of the series the wardrobe department stayed with what the characters were throughout the whole series!!!! Before Buffy was the Vampire slayer she was a prom queen, homecoming queen, cheerleader and was always going shopping for great cloths. Willow was this shy Cutie with the cutest sayings. Near the middle she was a witch and those were what witches wore!!! Dark and long skirts that flowed. Every time Buffy when to see her dad, they went shopping for cloths. So throughout the दिखाना they ended with their own styles!!!

well ya but that was part of willow