>>2366601OP here. It is a fetish thing, but I can explain it. The clothing, even if it covers nothing, implies that they intentionally put it on and are showing themselves off (often to an audience, implied or otherwise), with no regard for social convention or common sense. Just straight up nudity is more incidental and doesn't carry those implications, as there are certain everyday situations like bathing where someone would be nude, and you wouldn't have to take anything off in order to get dressed once you're nude, so the barriers to covering yourself are lower.
Part of it is also imagining the thought process that goes behind wearing it, which is enhanced the more cumbersome or elaborate the costume is while still being completely functionally nude. For example, in this pic, the girl actively chose to keep putting on the cowboy outfit after she neglected to wear underwear. At this point, she couldn't even put on underwear if she wanted to, because the other clothes are in the way. She'd have to take the pants off if she wanted to put underwear on. That's the part of it that's hot to me.
