I think it gives the fish a sense of security especially if one side isn't against the wall.
Although, having said that, the way I have my tanks set up, the fish feel the safest in the front bottom corners. I do this on purpose so they get used to me. I move my lighting all the way to the back so it's darker up front and I move all rocks and plants to the front. Over the first few days I see where they go for safety, then I gradually move all other plants/rockwork around the tank and leave their safety spot in the front. No more hiding fish for me! :smb: