Traditionally cotton is considered to be a stiff fabric, which means that it sits off curves in a rather unflattering way. It isn't particularly forgiving across the bust either.
Garments made up entirely of crisp cotton are more suited to straight figures, and actually enhance this body shape, providing a sharp, clean silhouette.
Curvy figures should look for cotton with stretch. Jersey cotton is made
on a circular knitting machine so is constructed very differently to stiff cotton. Often Lycra or elastane is added to provide extra stretch.