If I can't see through the vehicle in front of me so I can keep tabs on the vehicle in front of them, I stay back. I don't trust other drivers and I want to know what's coming up so I can react. It's irritating when the vehicle in front of you, the driver isn't paying attention and they have to break hard at the last second. I want to avoid any possible accidents.
However, the drawback for me hanging back is that other f'ing retards on the road think the open space between me and the vehicle in front of me is an open invitation to cut me off so I have to also be on the lookout for those morons.