It's "rice" because it's asian; it's a derogatory term used towards people and their cars. When I was younger, this term was used against asian drivers and their asian cars - and it was not a compliment.

Looking at Urban Dictionary I see no mention of this anti-asian side of it, but it was there when I was growing up. Maybe others can chime in with their experience, I imagine it wasn't the same everywhere.

Not implying the people using it here are being racist, I don't think they are aware of what I'm recalling here.

Think of the movie Fast and Furious: Tokyo Drift. It's used to describe unnecessary modifications to a street racer (led lights, decals, etc...) that was mockingly called "ricing" because it was prevalent in the asian street racing communities. (rice eaters...har har har...)

I thought I was the only one who cringed whenever I heard that word. But this thread is making me realize I'm not crazy.