Of course it's just for publicity, and it works...
And Adele has never been the subject of more articles than about her weight loss. Papers publish what sell, or what people click.
If no one gave attention to "barely there dress", the celebs would wear something else...
But frankly, with a body like this for most these women, they might as well make the most of it. Would be a shame to hide them, even if I personally would prefer slightly different gown, but I am not the one wearing them.