The reasons are a simple to do it yourself fashion.
You get what you want, when you can not afford to wear.
You can create your garments fit the body, giving a custom fit.
You get good coverage is made, that no one is going to be seen in.
There are many patterns to choose form, and if you get a mixed pattern pieces together and you design your own clothes, but I will not get very far out. If you are a beginner or your sewing skills are limited, it is available and try your hand at simple patterns that make building your own wardrobe.