Regional preferences. You will find a lot of Western hunters that do not load the chamber until they see game. In most of the Eastern states the custom is to load the chamber as soon as you step off the road. Lots of exceptions, but this is the way I see it. I've seen some hotly debated threads among folks who feel strongly both ways.
As a hunter safety instructor we have always taught that if the terrain is likely to result in a fall, when crossing a fence, ditch, or climbing into a stand the chamber should be unloaded. That is how I do it. Normally the chamber is loaded, but it is easy and fast enough to open the bolt, remove the round from the chamber, push it into the magazine and close the bolt on an empty chamber until the obstacle is crossed. Once on fairly good terrain the round can be rechambered.