generally speaking many gun owners do not reload and any advantage is lost. They are also the type who enjoy a few worthy firearms that are the most practical to them.
This type of person needs not to waste money on a PCC if he already has a decent semi auto rifle. There are AK's and similar rifles running lower than a grand, and ammo for these rifles are practically the same cost as common handgun rounds (really talking about steel cased practice stuff here...the price on brass cased ammo is devastating
)
Owning and shooting one for fun is a whole different story. I can't argue with that.
Speaking of 100+ years ago, I figure back then people liked the idea of one round for handgun and rifle because of two reasons:
1. Ammo in certain parts of the US were hard to come by. Getting two different types of ammo, especially if one was particularly less popular and therefore, less supplied, was not an option. They also didn't have the massive logistics capability we have now to supply ammunition.
2. Semi autos weren't around yet. You had your revolver and repeater. Shooting a "controllable" round in a revolver didn't make any sense. 99% of these revolvers were single action and even you got back on target quick, you still have to cock the hammer manually.
So it makes plenty sense to fire the biggest round you can handle in a revolver that you can also use in a rifle. That my best guess on the subject.