When my Dad started shooting High Power matches, you could not buy accurate enough ammo for any price, especially for 600 and 1000 yard matches. When I started shooting in the matches, it was only natural that I handloaded. Except for milsurp, I never fired a factory round.
Later he hunted in Africa and loaded .300 Wby because you could not get them with Nosler Partitions.
Later, I hunted in Africa. I loaded .375 and .458. You could not get North Fork solids in .375 (or any other flat points) and .458 factory loads were loaded to 2040 fps by the factory. I could get 2200 easily with handloads.
At one point I had a 6.5x54mm M1903 Mannlicher Shoenaur. You simply can't buy ammo. Further, this rifle had excess headspace and I had to fire form cases.
Finally, I shot matches with a 6XC. I had to fire form cases from 22-250s.
After all this stuff, I can say that no factory round has ever polluted most of my barrels!
Now I shoot mostly shotgun. I only reload 28 gauge because you can buy 12 and 20 cheaper than I can reload them.