I think one of the best things about handloading is the ability to throttle your loads. If someone has say a 30-06 and buys factory loads, they're most likely going to be medium (lawyer safe) loads with bullets selected to kill the average species that round is typically employed for (granted factory offerings have certainly expanded in the last 10 years...). If he wants to hunt a different class of species, he needs a different cartridge.
If this same fellow handloads, he can load down some cast/trailboss rounds for the grandkids to shoot off the deck with, some fast 110gr varmint medicine, a moderate, 30-30 velocity, load for his 14yo niece's first deer, and a 210gr moose thumper for that trip to the Yukon... Same gun, very different experiences.
I started butchering my own game ~5years ago and discovered just how much meat damage my bullet was doing (simply skinning out an animal and seeing the entry/exit didn't reveal 90% of what a bullet had actually done compared with separating the muscle groups when butchering). I did some research on meat damage/bullet selection and was struck by something the flint lock crowd kept saying about "near zero meat loss".
My growing theory is that, with the advent of smokeless powder came the need to toughen up projectiles to handle the increased velocity. In doing so, rainbow trajectories flattened out over night and bullets suddenly needed to be engineered to expand upon impact, and yet penetrate with out breaking up. The faster we went, the flatter we got, and the tougher our projectiles became(necessitating velocity to expand effectively).
IF one didn't need the range, thereby not requiring the flat trajectory, and IF he was to choose an appropriately 'soft' projectile, they could go significantly slower, producing less muzzle blast, less recoil, using less components and damaging less meat.
To this end, I tried backing my load down a couple hundred fps for the next season and found it MASSIVELY reduced meat damage while killing just as effectively.
Bear in mind, I'm hunting in deep bush. I think the farthest shot I've taken was about 120yds, with 90% of my shots being 50-70yds. Trajectory isn't an issue in this scenario.
For someone hunting across a coulee, I'm talking utter nonsense but again, handloading allows me to tailor a load to a situation.