The Semantics Of Arriving Fashionably Late

Everyone has heard of the term "fashionably late." Yet what does it mean? Why do some people show up fashionably late, when others just show up late, even though those two different parties showed up at the same time? What determines whether or not being late is quote-unquote fashionable? This tries to put it into terms that are unnecessarily confusing and contradicting, but that are meant to be humorous, and if you can dechipher them, DO actually explain the determining factors.