Because of a lack of life experience, newbies are unaware that hunters actually harvested deer with one shot, fifty years ago.
And many of the now modern bullets weren't even available then.

Of course, newbies are keenly aware of the protective armor that deer have started wearing in the last ten years, protecting them from bullets. The older hunters seem to relay on their ancient memory of shooting a deer twenty years ago, and tend to rely on older, less expensive bullets.