The difference between shooting on the range and shooting in the field, is time. On the range if you have any time constraint at all, you know how much time you have, and you shoot as quickly as you have to, in order to finish within the time allotted. Its not that you don't have time in the field, its that you don't know how much time you do have, so you prudently shoot as quickly as you can shoot deliberately. You can do everything right, but its time that defeats you, if the game moves before you can fire. So you train to make your shot in the shortest possible timeframe, from the moment the target becomes available.
Since time is the variable that most likely defeats us, prudence suggests that the faster the rifle is cycled and readied to make the follow up, the better. Perhaps you'll hunt your entire life and never have need of that skill, or you might need it next time you're out. Regardless, its a valuable skill to add to your tool box, and it boosts your confidence knowing that you can solve any problem that can arise. As an example, one of the most difficult problems to solve is that of a target moving rapidly towards you. The tendency is to shoot where the target was, rather than where it is. Given such circumstances, its not unreasonable to assume that a fast follow up is desireable. Why not just shoot a semi-auto? Well, cycling a bolt gun gives you something to do while you'd have to wait for gas to cycle the action for you, and its only recently that gas guns been equipped with triggers that are comparable to those of a bolt action's.