Girdles are designed to flatten your tummy and smooth your hips and derierre eliminating any lumps and bumps so your clothing drapes beautifully giving it that 1950s polished look (or in modern fashion, a couture finish). While they will tame your curves a little, their main job is to provide a smooth foundation for your outerwear.
They come in especially useful if you wear vintage clothing. Fashions from the 1950s are now 70 years old and those seams and stitches are getting old!
When you try on a dress or skirt it might fit perfectly in the changing room, but when you’re going about your day to day life, bending, sitting and eating, or simply the time of the month, your body will change. Wearing a girdle will give you just that little bit of leeway to prevent excess strain on those vintage seams.