A few years from now, perhaps around ten years or so, after first contact with star-travelling aliens, humans have acquired FTL and other technology making a new diaspora of humanity to the stars not only a feasible possibility, but given conditions on Earth, a highly desirable course of action for a great many.
It stands to reason that the various cultural groups would each set out on their own, to get them away from their cultural enemies and allow them to set up 'ideal' societies. Some would no doubt embrace the new technologies the aliens made available, while others may well choose to eschew high technology.
Let us further suppose that we have a cultural group that currently places a high value on body modesty for religious reasons, where going about displaying any more skin than necessary is socially unacceptable - some extremist sect derived from Islam or Judaism perhaps - which might emigrate from Earth with the intention of practising their particular religion and following its requirements with more rigor than possible on earth. Additionally, these people want to abandon the high technology to which the aliens have exposed humans - since many on earth are in favour of the alien technology, they must move to a planet over which they have sole control.
This means that there has been no major terraforming effort - that would require using the technology that these people would rather avoid. The environment therefore is a naturally-occurring oxygen-nitrogen atmosphere world in its primary's goldilocks zone, with very roughly 1g of gravity. Of course, to get an oxygen atmosphere, there must be pre-existing native life, and to be able to eschew the unwelcome alien nanotechnology, that life must be reasonably compatible with terrestrial life.
What conditions on the single particular planet that this group colonises, and/or mishap or miscalculation in the colonisation effort could force them to practise universal nudity, at odds with their beliefs, within a short period of time after arriving?
The reason will have to be either environmental or ideological - these colonists (or at least their leaders) eschew high technology prior to or immediately upon arrival.
The more powerful aliens aren't interested in slaves, in fact the whole first-contact was grossly mismanaged, and the aliens are now reluctantly in the same position as Europeans making contact with much more primitive natives, who have got hold of European technology, at the cost of the natives' society disintegrating as they argue about how to use it. The aliens want nothing more than for humans to get over their juvenile societal upheavals and to become mature equal partners in trade.
I am looking for a reason for the colonists to want - or at least have - to practise nudity across the entire habitable surface of their chosen new world. I don't mind if the change is ideological, as long as it is one that would fit with any current Earth religion that currently practises moderate to extreme body modesty, or if it is imposed for other reasons. Any answers suggesting an ideological change must support their answer with justification for a relevant example real-world religion's followers to make such an ideological change. It would need to be pretty convincing, as many religious people will do the most impractical things because their religion demands it, and these colonists are all pretty fanatical, or at least most of them are, and the rest can pretend to be just as fanatical really well, otherwise they wouldn't have been invited to come along.
An ideological change in these circumstances would be pretty unlikely, but if there is very good justification then I'd be interested. Otherwise, that just leaves environmental or accidental reasons, which would be just as good - it would be interesting to explore the deep conflict between religion and necessity or disaster management.
I would prefer if the reason was not that "The local sentient species insists upon it", as I don't want to introduce yet another sentient species in this context.
Finally, if an answerer believes that there is no reason that would make the majority of the radical muslims/jews/whatever abandon their clothing in order to survive or avoid extreme discomfort on their new hell-world, or that they wouldn't find some way to cover their nakedness even in the face of extreme shortages caused by accident or mismanagement (like making clothing from food, rather than eating it), I'd like to know that too - it would be interesting to explore a world where all the fanatics either died out or go about in daily torment because of their beliefs.