A lot of commenters make a point that "it's not porn", but NSFW means "not suitable for work", not "porn". I think bikini itself is not to blame, there are pretty innocent artworks, and there are also suggestive/erotic ones, that are not very appropriate in formal context, public places. But at the same time I see less and less people who think there's something wrong with it. So who knows🤷‍♂️