Probably a dumb question, but how is raindrops on a canopy like that RB one any different than raindrops on a helmet visor? Whatever teams are doing currently to deal with rain is probably what they'll do with a canopy like this. It's not like they're using tear offs or wiping it off with their hands every 10 seconds or something.

probably a driver will be saved by it someday. but the wheel may bounce back, injuring spectators.

A wheel may bounce off the side of a car, injuring spectators, it might bounce off the roll hoop of a car, injuring spectators, etc etc. If it bounces off the canopy it has already saved a driver, so who gives a fuck where it goes next?

How is that better if it bounces off after having already killed a driver? That's what happened in the Wilson and Surtees fatal accidents. The difference is that the driver was dead already. What about the stray wheel bouncing off a wheel?

Your arguments only work if you consider that the helmet/skull deformation absorbs more energy than a canopy, and would make the bounce less high/fast than if it hit a harder part of the car, but that is a terrible way of looking at things.

EDIT: sorry Reece I misread your comment, thought you meant the opposite, but I'll keep my reply because it's funny to imagine how desperately misunderstood and aggressed it will feel to you and other readers, before coming to the EDIT part.