Actually, they do. They all have 'governers' in them. Not one manufacturer (of normal cars, supercars need not apply) puts out a vehicle that doesn't have a speed limiting device.

Even the 350Z has one.

Why? The tires. Sure, they look beefy, but they're only speed rated to a certain point. Past that, the construction of the tire cannot hold itself together. It's own weight will tear itself apart.

When Nissan puts a tire on a vehicle, they program the computer to not surpass the limits of the vehicle, and that includes the tires.

So what if you could put different tires on it. So what if you want to put the bottle to the engine. So what if you hammer down going down a mountain pass. Nissan doesn't care. They'll look out for your safety, even if you won't.