99% of 4 wheel vehicles don't have forks, that's a big difference.Can you say 99% of all 4wheel vehicles ever? I cant think of higher forces on a 250-700# bike ever being greater than a car?? It is and was a pretty sweet system, just mostly new and different, and maybe better...
Bicycle forks are very light, I imagine you don't feel a balance difference on that Cannondale? On a motorcycle you'd have a lopsided setup that either needs to be made of very expensive materials that are strong and light weight (same as that Lefty setup), or it would need a counterweight since motorcycles are balanced upright, which isn't the case for 4 wheeled vehicles where there's one on each side.