So you're telling me that UG & UG 2 didn't represent the (then underground) import car culture of the late 1990's and early 2000's and that EA was being sarcastic? Look at the photos below. They're from Hot Import Nights events, circa 1999-2003 when the import car culture was still an underground thing.
The problem is that from today's perspective what we see on the photos above is rice. Riced out Civics with wild bodykits, empty NOS bottles and playstations in the interior. And this what the underground import car culture back in the day was all about. Fast & Furious movie in 2001 brought JDM into the US and helped the import cars get mainstream. This is when people started going crazy about "JDM", Supras, Skylines, VeilSide kits, etc. Influence #1.
Another influence was the DUB culture. Huge chrome wheels, spinning wheels, LCD's and billion megawatt audio setups, SUV's.
EA went a little bit crazy with the modifications, but you can clearly see the base line.
My point is that what we see now as rice (the vehicles above) was cool fifteen years ago. What we see as cool now will be rice in a decade. Most of the mainstream styles I mean. NFS 2015 seems to be heavily based on "USDM". Though we have yet to see VIP style.
Funny thing is Americans are going crazy after what the Japanese have been doing for quite some time and then the Japanese take it back to Japan and back and forth, but that's for another discussion.
P.S.: And no, a slammed Rocket Bunny BRZ with stretched wheels is not a track day car. :p