I suppose if you carry a gun you would likely never have to fight. You'd always be able to deter your opponent, or if that fails, shoot him dead. But say it's a drunk fan at a ballgame accosting you, and you either don't have your gun on you, or you don't want to risk accidentally hitting other fans with gunfire. Situations like that may require you to fight someone without a weapon of any sort. It's all hypothetical, but certainly possible.
That's why I have trained in the wide range of unarmed skills that I have done (as rare as a no gun location is in my life). It is also why I nag on the need for everyone (aikidoka included) to train with a worst case situation style of training. Start on your back and learn to stand up when someone doesn't' want you to. Then learn how to do all that stuff that looks good in demos.
I'm actually trying to get back into an aikido gym right now after years of judo and bjj. It has nothing to do with self defense. it has everything to do however with just doing something different for a while and focusing on something I'm not very good at. (I'd must rather do something I suck at then something I'm good at).
As a side note, I train more often to use, control, and keep my pistol than I ever have at unarmed defense.