For the same reason anyone does anything to be different or individual. Some people (especially the younger ones) aren't into the "cookie cutter", "go with the crowd" blending in mentality, and that's a good thing. That mentality is what leads to new innovations in every field of thought.
If Elon Musk had stuck with the crowd, we wouldn't have the Tesla Roadster or Space-X program. If Nikola Tesla hadn't swam against the current, our entire modern world wouldn't exist as it does. Internet? Gone. Power grid? Gone. Radio? Television? All of the AC innovations like indoor climate control, wifi, refrigerators in every home, lighting up the night, that bone stock Boxster, advances in math, science, medicine...all innovations by those that chose to do something different with their individuality and creativity. Going with the current is not human nature.
With all that said, I kept mine stock for the first 1.5 years, aside from the rear emblem which was broken. I'm also no spring chicken (37 next Monday).