I've seen farms use canopies as bird deterrants. I've also been told they reduce the amount of particulate on the crop and makes it easier to get good results for selling for grocery store food and stuff. But my family farmed livestock and I was mostly the city cousin - so I'm never 100% sure how much of that kind of story is true.

I've heard that in cold places, canopies are relevant for keeping sleet/frost/etc down as well - reduce falling moisture to prevent impact damage to delicate crops. But I grew up in the sub tropics so it wasn't really a thing for anyone I knew personally.

From pure prejudice, I would have thought shaking the water off like that would be about keeping the weight on the canopy down so it doesn't get damaged. I would have guessed that any water landing on crops would be an incidental benefit.

I'd love to know more about the actual use case in the OP.