> I would not expect a trip on the highway without traffic to be better at all with a hybrid car than with a gasoline car.
Hybrid systems allow the gas engine to (essentially) always run at its ideal speed if it is running at all, storing extra energy when less is needed and drawing power from the battery when more is needed. On an idealized highway drive, with cruising speed at exactly the pure gas car engine’s ideal speed, with no variations due to turns, hills, traffic, etc., this is no benefit, but real highway driving tends to differ from this ideal enough that hybrid cars have benefits even in freeway driving.
This is true of a second-generation hybrid, like the BMW i3 (with range extender). A first-gen hybrid, which is most hybrids (including the Infiniti QX60, the BMW 3-series (not i), the Mercedes E-class) still power the wheels primarily with the gas engine, and only use the electric engine in certain reduced circumstances. With the gas engine directly driving the wheels, you don't get a lot of benefit from the hybrid except in start-stop conditions.
The first-gen/second-gen language is a bit odd. More common would be “mild” vs. “full” hybrid, but most hybrid cars sold, in the US at least, are full hybrids (what you call “second-generation” hybrids); Toyota Prius nameplates alone account for almost half of all hybrids that have been sold in the US, and all of those are full hybrids.) It may be that mild hybrids dominate if you are counting individual models, but certainly not if you are counting vehicles.
Hybrid systems allow the gas engine to (essentially) always run at its ideal speed if it is running at all, storing extra energy when less is needed and drawing power from the battery when more is needed. On an idealized highway drive, with cruising speed at exactly the pure gas car engine’s ideal speed, with no variations due to turns, hills, traffic, etc., this is no benefit, but real highway driving tends to differ from this ideal enough that hybrid cars have benefits even in freeway driving.