Higher polycount does not automatically increase details. While round-shaped car like RB4 obviously could use little bit more polygons to make it look less blocky, most cars are fairly boxy by design and just increasing polycount without adding new details is pointless.
Now this leads us to the fact that most cars in LFS are based on fictional design with some small resemblances to various real cars. To add more details, you must first do some design work and sketches to figure out what works and what doesn't. This takes a lot of time and it's pretty much trial & error until you come up with something that looks great, even talented designers come up with horrible stuff once in a while and as for those without talent....well, you can look up those bodykits in last few NFS games.
Now this leads us to the fact that most cars in LFS are based on fictional design with some small resemblances to various real cars. To add more details, you must first do some design work and sketches to figure out what works and what doesn't. This takes a lot of time and it's pretty much trial & error until you come up with something that looks great, even talented designers come up with horrible stuff once in a while and as for those without talent....well, you can look up those bodykits in last few NFS games.