This is a good point, though I woudln't even say they are optimized for stop and go traffic. Hybrids are far less wasteful in stop and go conditions than other cars as they don't need to idle the engine, and they can reclaim some of the energy wasted from braking. However, even with all that, gaining and losing momentum repeatedly is inherently less efficient than steady-state driving, where hybrids, and any other car, will do better. Also, hybrids do better than all but the most efficient diesels in highway driving as well (in part because there's more energy per gallon in diesel fuel).

One of the points I've repeatedly seen criticizing hybrids is that their regenerative braking only kicks in stop and go conditions, and that on the highway, all the battery equipment is essentially dead weight. (Of course at a steady speed, the extra inertia is irrelevant) Hybrids benefit efficiency in more way than just regenerative braking. One of the major advantages of hybrid power is that the torque available in the motors allows a much smaller, more efficiently tuned engine to achieve the same performance. This saves lots of fuel at steady speed cruising by reducing pumping losses that would be there in a normal gasoline engine (Diesels also have minimal partial-throttle pumping loss) The larger battery packs also allow the ability to "balance" loads on the engine caused by elecrtical accessories, power-steering, headlights, and air-conditioner, by charging more under light load, and backing off under heavy load.