The simple explanation is women seem to operate in a dichotomy. But they don't. Remember they feel rather than think because they are ruled by inconsistent neurotic impulses. It makes them hard to predict, but logical or consistent mind can understand their motivation.

The Marketing Basics

The basics of women's clothing is it is priced to be expensive because they egotistical believe they are worth the money.
It's thin and poorly made because quality doesn't matter, they won't wear it more than a dozen times before it's replaced.
It has no useful function or purpose, like pockets, because the wearer doesn't have to do anything so they don't carry anything.
It's designed to be layered to sell more clothes and accessorized to sell expensive jewelry.
Sizes are purposely inconsistent, if you find a store that sells "mediums" that fit you then you'll always go back to them instead of admitting you are a "large".
It's all just bottom line marketing, so you should pick up in this and the rest fairly easy.

The "inconsistent" Part

It's tight by design so the women can brag about her looks. This is done for three reasons.

1. Her self. A women always wants to feel good about her self. Not neutral, not indifferent, not unconcerned. Good, great, & excellent. This is also why they will insist on wearing makeup even if they won't be meeting anyone. Putting effort into controlling their looks makes them feel good and powerful.
2. To insult her friends, because it is done for them. Friendship in the selfish & emotional is not about helping each other. It's about feeling superior. - ie "help" is done to demonstrate superiority. - Showing off your sexy body to other women is a power move in a game of never ending plays, and winning makes them feel good and powerful.
3. Lastly it is done for men, because it is done for them. It feels good to be wanted and powerful to control the gaze of men. But it has to be subconscious, not conscious choice. Men that act on this enter a second ring, do they like the guy? If they don't, its harassment to even show any interest they are expected to control. And if it is a man they are interested in, then their clothing and their body and their personality and their intelligence has attracted a man they want. And that makes them feel good and powerful.

And that's pretty much it. Now it's time for a test to demonstrate your understanding. Most clothing designers are women, not men. They design clothing marketed to women, not what men think women should wear. So if you design something stupid, ugly, & useless. Then pay a bunch of models to show off to a bunch of your "friends " in a tax write off. How does it make you feel when another women buys your obviously flawed product?