Modern panels are wired so that they're not quite so devastated by having an edge of the panel occluded. You can observe this with newer folding panels as well; they're often wired such that only a half or quarter of the panel being exposed leads to a linear reduction in output as opposed to a catastrophic failure.

Besides, it's not like farming is human-labor free. It's certainly comparable human labor to imagine keeping solar panels relatively dust free compared to growing strawberries.