Absolutely. They can share accessories, magazines, and ammo. This is especially applicable if one has to make a trip to a gunsmith or the factory. Also, one can be kept in one place, and the other in another place, so one disaster or other event does not claim both, or prevent access to both. For example, I have one BLR securely stored in a quite safe place away from my home, at a higher elevation.
One rifle can be set up with a long-range scope, and the other with a shorter-range optic, or iron sights. If one goes on a hunt a long way from home, taking two identical rifles means that if one suffers a broken part or worse, there is another familiar rifle handy. One extreme example would be a horseback hunt in the backcounty.
Lost luggage is another factor. If my wife and I each fly with firearms, I can carry one of her rifles, and she can carry one of mine. One lost gun case will still leave each of us with a rifle.
Any firearm I really like, that I use for serous purposes, soon has me looking for a spare. I have more than one each of: Remington 870 pump gun, Browning BLR, Mini-14, SIG P229, GP100, and SP101.