Voodoo hips

Wait some are labelled according to waist and leg length. Still doesn't work for some reason though.

True! That's why I wear mostly stretchy leggings. And also my hips are two sizes larger than my waist so most non-elastic pants don't fit me at all.

gladly, it's very socially accepted for women to wear other things beside skinny jeans.

It's called vanity sizing. Many brands label the size this way by reducing the size on the label on the garment to make you feel better when you're trying it on in the dressing room, thus increasing your chances of buying that product. Unfortunately, there is no coherent understanding between the brands regarding how to reduce the size, leading to misleading garment sizes across other brands.