Why put a "fairly involved" solar system on top of a truck when you could just put it on the ground in a sunny spot? Maybe solar farms are too boring and effective to excite investors...
a) put solar panels over the truck
b) put solar panels in a fixed spot, where it's easier to use big panels, maintain them, avoid nasty vibrations, and transport the energy to a charger.
In b) you get more energy, even after transferring it to the truck. So you can use the extra energy to power other truck or a home or something, and then avoid burning fossil fuel and then saving the panel.
The option b) is more environmental friendly.
Somewhat related: https://what-if.xkcd.com/17/ Grass is the solar panel of cows.