Well, let's see...
The majority of animals I've taken have been less than 200 yards. Having said that, no, I'm not going to make my sheep or goat rifle a 45/70. Sometimes cover gets pretty sparse above the timberline. I have taken game just over 300 yards before, my priorities have changed now. The hunt is the thing. My pleasure of the hunt is the stalking or still hunting to within a reasonable distance. Reasonable. What's that? Depends on who you are, where you are and what your skills are. I don't think there are a lot of people in a hunting situation that can make a 400 yard shot. I won't take that shot. I seriously doubt I would take a 300 yard shot anymore, even though I practice at that distance quite a bit. Just too many things to go wrong at that distance. Besides we are hunting, not just shooting. If there is animal out there that I can't get to 200-250 yards of, well, he's better than me and wins the hunt I guess. 200 yards in an area with sparse cover is pretty good stalking, and if you can get closer - you should do everything in your power to, but sometimes you can't (Ever tried to stalk across a glacier?) I've never shot a moose more than 100 yards, I've never shot caribou more than 150 yards, never took a shot on sheep or goats past 225, but I have shot deer at a little longer. I won't anymore, but I have. There's no need to, I feel confident enough that I can get that close to my quarry on any given day. If I don't today, I'll try again tomorrow.
I think there are three reasons why the whiz bang magnums sell so well.
1. That is what is being marketed. Jack O'Connor wrote about great hunts shooting game at extreme distances with flat shooting cartridges and that has embedded itself in the American hunting psyche and gun manufacturing psyche. Alot of people want to be like Jack.
2. Fear. What if? What if that "book" buck is 350 yards away across an open field? Too much emphasis is placed on scoring if you ask me. I've never had animal scored, I've never turned an animal down because I didn't think he would score well. Seems like everyone wants bragging rights.
3. Pride. "Yeah, I killed that deer, moose, sheep, whatever, at 600 yards." I'm the best shot there is. Blah, blah, blah.