In the effort to achieve expediency, Tesla has not prioritized the solar canopy on superchargers. In my limited experience of exactly two superchargers in Texas, San Marcos has good solar access while Columbus does not (trees). Somewhere down the line they might prioritize solar access, just like they might prioritize visibility so that beautiful cars charging for free in direct sight from the highway would be a great way to 'spend' an advertising budget. Again, San Marcos and Columbus are not visible, tucked behind buildings and a couple hundred yards off the freeway. Expedient, cheap (free?) land, but not yet prioritized for solar or advertising. Coming, I hope.