I would hope/guess that Honda's engineers would have a good reason for this, possibly the battery will last longer if fully charged. Also, you are simply storing energy that will be used later. I'm probably naive, but I would think if Honda could eak out a couple of more miles/gallon by disabling it at speed on the highway, they would have. I barely notice it on the highway, seems like it regeration occasionally comes on for a few minutes, but is mostly off, unless the battery charge gets low from a lot of city driving.