Many fashions and artworks originate as copies of practical objects. Why? Because any form of optimized design is intrinsically esthetically-pleasing, and a great starting point.
Countless genres of art start in appropriating objects long incubated in subcultures for originally practical purposes, often becoming fashionable and collectible because no longer practically relevant, such as fancy watches. This seems a little odd, and leads to weird economic situations where brands bend over backwards to try to maintain ‘authenticity’ by, say, showing that some $5,000 pair of sneakers sold to collectors has some homeopathic connection to a real athlete.
With an infinite design-universe to explore, why does this keep happening and why does anyone care so much? Why, indeed, is l’art pour l’art not enough and people insist on the art being for something else, even when it blatantly is not?
Because humans respond esthetically to not simply complexity or ornamentation, but to the optimal combination of these in the pursuit of some comprehensible goal, yielding constraint, uniqueness, and comprehensibility. A functional goal keeps artists honest, and drives the best design, furnishing an archive of designs that can be mined for other purposes like fashion.
For that reason, the choice of a goal or requirement can, even if completely irrelevant or useless, be a useful design tool by fighting laziness and mediocrity.