It takes very little water, especially at night, to totally obscure road markings. If we took that advice, then you couldn't drive on rainy nights at all. Just

It takes very little water, especially at night, to totally obscure road markings. If we took that advice, then you couldn't drive on rainy nights at all. Just like the GP said, lighting can make the situation worse by reflecting off the water. The signage is a great backup in this scenario. It's not clear to be what else you think the water might be obscuring in this scenario. Maybe potholes, on poorly maintained roads you're not familiar with? At least where I live, that's not a problem.