I've done some research on this. For one thing, cobblestone roads wouldn't last so long under the weight and shear forces of modern vehicles. Y'know when Wile

I've done some research on this. For one thing, cobblestone roads wouldn't last so long under the weight and shear forces of modern vehicles. Y'know when Wile E. Coyote skids to a stop so hard that the road under him wrinkles up like a rug? A loaded semi truck braking hard can actually make asphalt do that, just as an example of the kind of forces involved. For another, cobbles that are even a little bit wet become slippery deathtraps at even moderate driving speeds. Even when they're dry, highway speeds are going to be very uncomfortably bumpy. Hard on people and hardware both. Basically, a good driving road requires a surface that is extremely smooth but also somewhat tacky, and that really limits what other properties it can have. You can't build something like that out of durable stone.