Why doesn't Prius Prime drive train battery trickle charge engine battery?

The Prius Prime was never meant to be a fully Electric car. From a scientific point of view, the gas will get old. You should try to use your gas once in a while. Let me tell you about my little trick to get more distance out of my electricity. Electric cars will consume the most power when accelerating from a stop position. It does not matter what brand of electric vehicle you own. Taking off from a stop position at a light uses the most power. In the Prius prime, we have the luxury of using gas to take off from a stoplight, and when I get to your desired speed, I switch back to electric. Benefits are: My gas never gets old, and I get to travel furder on my electric.

Frank, so how do you do that exactly? I did not know I could choose to disengage the electric power train! Can you give me a step-by-step?

For the average user and in the words of my wife, my method is a pain in the @@###. However, if you would like to burn a little gas in a useful way, this is how I get the best of both worlds. When I am at a stoplight, I switch the middle button from EV to NV. Doing so will turn on the gas. When the light changes to green, I accelerate on gas to keep up with the flow of traffic. Once I'm up to my desired speed, I switch back to EV. No need to do this if you do not have traffic behind you. I found this YouTube video. https://www.youtube.com/watch?v=STtk3NM9qno