One fact that a person needs to consider is that when muzzleloaders were the common firearm and repeating rifles came out many people considered them unnecessary and wasteful.Then smokeless powder cartridges came out and they were looked at in the same way by many people.Then came the 308win and 30-06 which again were considered overkill by some people.When the 7mmremmag came out the situation was the same.At each change some people welcomed the new cartridges while others complained that they weren' t necessary.You can argue that the 30-06 is all that is required because many hunters still kill their game with the 30-06 but then again someone else will answer that the 30-06 is not necessary because they still kill their game with the 30-30.A muzzleloader hunter can then argue that all that is required is a muzzleloader since they killed game for hundreds of years.When I grew up the most common cartidge in use in my area was the 303 british.This was not because it was the most efficient cartridge but because they were readily available for a cheap price as surplus guns and ammo from the world wars.Therefore just being the most common cartridge does not make it the best cartridge.So one cartridge having killed more game than another does not mean it kills game any deader or any quicker than the another cartridge.
The bottom line is that a person should use what cartridge they like as long as they shoot it well.One should not try to tell others what cartridge is necessary and what cartridges are not necessary.There are some poor hunters using magnums and there are some poor hunters using 30-06' s so judging a hunters skill by the cartridge that he uses is not an intelligent move on anyones part.