True enough, although I have a square, shapeless figure, "tarping over" the issue feels nice until you see a picture of yourself from the back. :/But if your body shape already looks like you're pregnant or worse, there's no point in trying to look 'slim' and most of us know it. We're not fooling anyone, but at least the fat bulges aren't all on display to be gawked at. They help disguise what's below the empire waistline, add at least some shape to an otherwise shapeless body, and direct the viewer's eye to better features above it. That's a small but needed boost to confidence and body image. Besides, they're comfortable; no binding or pinching.
(Stated just so skinny people can maybe understand why fat people might choose unflattering clothes. It's all about comfort and self-confidence and has little to do with impressing others. Did you ever notice a fat man wearing overalls? He's not trying to hide his belly bulge, he's just trying to keep his pants up and prevent plumber's crack. LOL)