It's red. It's fast. It's Italian. It's a Ferrari! Now if I had the choice between teleporting instantaneously between point A to point B or take this baby out for a ride, I'd choose the car. Then again, who wouldn't? Nephrite takes this baby around town when he's crusin' for victims, making a quick stop at the Mall (to look for Sailor Moon), or just to drive really fast around town! And hey, every villain wants that.
So what does the car say about Nephrite? Well, it's a Ferrari, so he's got money. A lot of money. It's probably the most recognizable and popular Ferrari, so he wants to fit in--to display himself as something everybody wants. It's got a big engine and it's red--well, we don't have to be Freud to spell out what that's saying, but I'll just say that he wants to pick up chicks. In short, the car is an advertisement to sell himself to the community as a virile young and successful business man. Ah, boys and their toys.