I didn't say it was "preferred", merely implied that it was a concept.
It's extremely dated information. I can't find the the book to quote from at the moment but I believe it was from this 1966 book:
Author of The Weapons of World War III and The Crime Confederation
www.goodreads.com
The book is about then new theories behind the adoption of then cutting edge small arms such as the M16, the M26 grenade, etc. Among other things it discussed the reason why smaller caliber rounds were gone to: been counters figured it takes X amount of rounds fired to account for one enemy hit, so the ability to carry more ammo was better. Hence the move to the 5.56.
Now that I think about it though, I should have said "gov't bean counters" support the policy rather than "the military." And since when the book was written I've also heard first person retellings of difficulty in bringing down opponents on narcotics, both in Vietnam and more recently in the Middle East, with the new smaller caliber rounds
All of this is (at best) relevant only to military use, not hunting.