You have to remember that these guys are shooting a huge range of animals in terms of size, hide thickness, body cavity depth, distance of shot, etc. Here we have the ability to tailor our rifles, loads, and scopes to the particular type of animal and (usually) range we are hunting. In Africa, you quite often have maybe 2 rifles to use from pint-sized duikers up to pachyderms. Besides this, big bores really don't tend to kill quick, they simply put 2 holes in every animal - one in, and one out. This leaks blood, and ultimately kills. A .270 or .338 or whatever dumps a lot of energy into the animals that we hunt, but we don't deal with a lot of thick hides. Also, those wonderful whiz-bang controlled-expansion bullets that we use for hunting tend to work great, but sometimes fail. When you are hunting a Cape buffalo, a failed bullet becomes an EPIC FAIL. Thus, you use solids which always work, though not spectacularly so. BTW, I love big bores, too. My best is my .577 with a custom 685 grain mould, fun!