I’ll always have at least two rifles. When everything is fine, one is all you need, but when an accuracy issue comes up, and it will, having a second rifle instantly lets me know it’s not the shooter. Swapping scopes takes 5 minutes to rule out a scope issue. Worst case, a backup rifle saves an awefully lot of frantic messing around when something happens last minute before a big hunt. The guy who stuck a case in his rifle right before a hunt and broke the extractor trying to get it out, had to fix the rifle, identify why the case stuck, fix that, all in a matter of days.
Even if my trainer/plinker chambering were the exact same as the hunting cartridge, I’d have two rifles. The most accurate one I’d save for hunting and burn the barrel up on the other. When I had one good rifle and the barrel was used up, it was hard to send it off for another barrel with nothing else to shoot.
At the range it’s more interesting to have a second rifle to shoot while the other cools down. For some reason it’s all the rage to shoot until the barrel is smoking hot, even though it reduces the barrel life a noticeable amount. The guys that claim it doesn’t hurt anything aren’t volunteering to pay my gunsmith bills.
The final reason is to always have a loaner rifle I’m not worried about. The primary rifle shouldn’t get loaned out to anyone.