Hunters get to kit up in advance without the requirement to carry on with their normal everyday activities, day in and day out in full kit. They also generally ambush their targets instead of being ambushed by them. Rapid follow-up shots are generally less important, to the point that single-shot self-defense weapons are virtually unheard of while single-shot hunting weapons are not terribly uncommon.
The result is that it's quite easy to carry a very large and relatively powerful weapon while hunting and it makes sense to focus very heavily on the effectiveness of a carefully aimed single shot, taken under conditions which are, to at least some extent, the choice of the hunter. For obvious reasons, self-defense situations are very, VERY different.There is a lot of truth to this statement, however, missing is a reality in a situation where one is ambushed and must respond rapidly under extreme stress and likely under conditions chosen to favor the attacker and disadvantage the defender.
While it's important not to focus on capacity exclusively when it comes to self-defense, it's just as much of a mistake to pretend that never missing is a reasonable self-defense strategy.