It's rice because of how people use it. When a person takes a greddy or HKS exhaust with an oversized muffler (aka FART CAN), and puts on his civic... making the civic rice. Now, it's rice. The companies are not rice, what people do with their products is rice. Then the now full blown ricer, goes "Yo, dawg, I got my HKS exhaust straight up from Japan... for an additional 50 horsepower". That's just AAAAAAAAAAHHHHHHHHHHHHHHHHHHHHHHH. But, yeah, since this is not a car forum, I won't really go into that.

The movie comes into play as a catalyst of sorts, there were people who were modifying their civics before TFATF, however they were just mere modders like everyone else. After the movie the epidemic began. People realized that it's (supposedly) "cool", neon lights, Type-ARRR shift knobs, JDM mirrors, began filling up Kragen, Pep Boys, etc. That's how the movie comes into place. It basically made the current definition of "rice" just that.