That's because we're already at to the limits. There was a Moore's Law for the speed of transatlantic ships for about two centuries, and one for transatlantic flights for about half a century. (And I kind-of doubt Moore's Law will last for much longer.)

EDIT: though if you measure them in doubling times rather than in years, I agree that those for vehicles weren't anywhere near as impressive.

It's possible for a while, anyway; we're already reaching certain physical limits, and I suspect Moore's Law in the sense of shrinking silicon transistor sizes will be over in the near-ish future (order ~10 years).

It may just be that we started much further away from the optimum in this case than we did with things like motor vehicles (where there are fairly low limitations based on safety and human reaction times).