One can quote certain tribal cultures where it is socially acceptable, but D&D ain’t that, is it? At least not the part we have seen so far in BG3. Everyone else goes around fully clothed.
Clothing laws and practices depend entirely on where you are in Faerun, and what type of person you are. BG3 is set on the Sword Coast, which is roughly euro-centric medievalist, so in this particular case it's normal and proper for people to go about fully clothed. It would be different if it was set somewhere like Mulhorand, which is roughly ancient egyptian in flavour and nudity would be more common.
I also say it depends on what kind of person you are, and I mean that literally. Some races are more likely to get away with going partially or even full nude.
I once played a taur-type character (based off centaur), and the party came to the realisation in one session (after the DM mentioned it) that she never wore any covering around her tail end, something that I had never even thought about. She had been going effectively pants-less the entire time. It wasn't brought up after that, it just became a fact of the game.
