I'm with your wife on that. Why would anyone want more than one gun?I'm still struggling to convince the wife I need a second gun let alone a duplicate gun.
Find the gun you like and buy multiple copies.
Guns break. Just because you have A gun, does not mean your gun shall always run. The space shuttle went up like a bottle rocket, twice, your simplistic piece of steel and plastic will fail too.
Someone may take your gun (the police). Have another.
Guns are mechanical devices, they need maintenance, have spares while one is in the shop.
Fires. Have a copy off your property at relative (that you trust) or buddy's place.