Back when I had a Prius, I made a conscious effort to avoid using the brake pedal during the highway portion of my commute. It made a small difference to fuel economy, but treating it as a game reduced the frustration with stop&go traffic.

I don't think it's marginal since accelerating the car needs way more energy than fighting loses due to wind and tyre resistance.

Also, a bad driver mis-breaking trips the cars behind into breaking too, which multiplies the energy waste and may also cause accidents through fatigue.

Mare experienced drivers will give you more leeway to avoid tapping the brakes with you, or simply go for a staring overtake.