Solar panels are very cheap, and any modification, even just a moving cover, greatly ramps up prices. No, really.
We just need a lot of panels to generate significant amounts of electricity, which would necessitate a large cover or a lot of mechanisms - which would get expensive on that scale.
This might not be the case anymore, now that solar is dirt cheap.
But, as another commenter said, I’m onboard with any decision that scientists (including both energy and climate sciences) and engineers come up with working together.