The manga cover is one thing where the elf look like she's wearing a skin tight suit, but it's not like the artist can't draw fabric when you read it, it's just the underboob part that looks unnatural when it comes up.
I have no idea why they can't draw it to not shape like their cloth is fitting right under their boob like it got shrink after that one time they washed it and now the girls can't afford to buy a better one.