I've thought about this myself. There are only a few types of lobbies that actually gain traction. Even fewer gain traction with the enlighted upper classes of GTP: 450 PP road cars, 500 PP road cars, 550 PP road cars (if you use race cars, racing tires, or anything faster than 550PP, you're a noob), or prearranged league races of various types (often involving some kind of arbitrary stipulation or restriction, such as having a minimum lap time below which your lap will not count). Even out there on the open lobby scene, there's not much more: 15 million Nurburgring North rooms (sorry, I can't spell Nordschwhateverit'sspelledlike), cruddy TGTT free run rooms, shuffle rooms clean to dirty (that rarely remain good for long), NASCAR (usually dirty), cop rooms that fall apart quickly (if they were ever any good in the first place), cruddy drag/Wangan Midnight rooms, and more 450/500/550 road cars. And if the track selection is left up to the democratic process, you're pretty much doomed to see London and Cape Ring Full/Outside/North at least once before you get a track that's actually good for online racing.
As for those 450/500/550 road cars, those are annoying in other ways too. Because of the way the PP system works, torque and powerband are the enemies, which leads to obnoxiously precise power limiter/ballast abuse as well such unrealistic tuning techniques as leaving a used car's oil dirty and engine worn, or not fully breaking in a new car. Or perhaps just using vaguely unrealistic combinations of parts. All in an attempt to maximize the horsepower and minimize the torque/powerband width of your NSX/M3 E46/GTR/LFA.
Come on people...