I think a lot of people already had a 45 Colt rifle before they decided to try black powder. Or else they knew they wanted to shoot BP when they bought it but were unaware of the action fouling issues.
I shot a lot of 45 Colt BP in a '92 when it was my only rifle, but now that I have multiple calibers, my .45 '73 is strictly smokeless. I shot BP in it a single time, using 45 Schofield rounds (because it is a trapper and it is easier to load them) fully loaded with a 250 gr "Desperado Bullet Co." bullets with their "BP friendly" lube. Well, it was pretty horrible both in the bore and the action, so I'm sticking to the .38, 44-40, and 32-20 for BP. I considered fireforming some 44-40's to .45 but not for long as there is no need.