Originally Posted by ZeroZeta

Too serious but..

My hypothetical take on the OP is that it is a natural instinct to respond with caution when there are unknown variables or unexpected changes in the environment.

Notice how some people slow down if they are walking on the sidewalk and pass an ally, or if there is construction. Same thing.

Visibility may be limited up a steep hill, and there is higher probability of loss of control at an incline.