For example, if I were to see a suburban mother of three in rollerskates and a tutu, I would wonder to what degree her life choices were forced on her, what dreams she had that were put aside. Or if I were to see someone going full goth, extreme corset, platform boots, spikes and buckles everywhere, I would wonder about disfunctional family expectation or religious upbringing or such. Or if I see a couple being especially demonstrative, I would wonder who had told them they couldn't be a couple. Or a flamboyant homosexual. Or, ok, someone who wears plate armour more often than is strictly necessary.
It looks playful, or childish, or just aestheticly inexplicable, but I think there is almost always an edge to it of proving a point, of asserting their own reality, and in the background, someone who has hurt them.
In high school, one of my English teachers told the class she wanted to be a journalist, but that the relevant person (high school principal?) had refused to write a letter of reference because he didn't think it was a suitable job for a woman. This must have happened a lot in her generation and earlier.
This is not to say that every time someone wears something unusual it is an instance of this. There's a particular quality of being in opposition, of being extreme, rather than of following a necessary internal logic. The boundary is fuzzy.