I'm sorry, I know I'm going to get a lot of stick for this but muscle cars weren't meant for GT, old ones I mean, you know, the kind which gave American cars their bad name (which I hasten to add is no longer true)? Leaf sprung suspension, live axles, brakes made of the finest Camembert (i.e. cheese), weighing in at over 2000kg, aerodynamics of a brick... You can't deny that muscle cars aren't exactly in their element on the track, unless it's Daytona Speedway, they're generally the exact opposite of what you want for track racing.
So, what I want to know is where are all the British ultralightweights that are purpose built for track racing? I mean, there was no Lotus Exige, no Ariel Atom, no Caterham that you could actually use in a race, no Ultima GTR, no Radicals! Surely they deserve to be included just as much as the F1, LMP1/2 and GT1/2/3 cars, considering they are built to go around corners at stupid speeds, which they frequently do. Glad TVR made it in, though.
Of course, this thread could just turn into 'why didn't my country's cars get picked for GT4/5?'. It's a valid point, but unfortunately at the same time it's one with a very simple answer which has already been given. PD are Japanese; Japanese cars are their focus, I can only hope that now we have DLC they'll carry on developing cars for GT5 after the release instead of just working on GT6, maybe then we'll see more 'niche' (read: blindingly obvious choice) cars?