Having discovered that the necessary clothing was NOT available in shops or from other designers and makers, we move to making up things on our own.
The initial idea is to make something serviceable. Something that solves the need. For a pair of pants. For a skirt of a particular length, color, weight, to be worn with a particular jacket or shirt or coat, or boots. For a dress or a suit for a particular occasion. For a coat to go over something. For something to keep one warm, or cool. To solve the immediate need, even if it is very fleeting. A get up for a party. A costume for one holiday or another. An extraordinarily plain and infinitely useful skirt or pair of pants.
It turned out, and continues to turn out, that a thing which is serviceable for one occasion, even if it is very particular of an occasion and garment, will likely work for many other occasions. Maybe all of them. Probably all of them.