I'm asking this question for my sister, who bought some shapewear recently. She noticed at the first wearing that they are crotchless. (Apologies to those of you who dislike that word. I'm not crazy about it myself.) For those who have more experience with this type of garment: Are you supposed to wear underwear under them? Is the crotchless feature so one doesn't have to struggle out of the item to use the restroom each time? Many thanks!