I suspect that prospective buyers were concerned that the shorter barrel, with the more powerful cartridges would "not shoot as hard" (losing velocity due to the burning characteristics of black powder). Recoil might also be a factor with the lower weight, but I doubt that was the main reason, unless a shooter had an opportunity to try both rifle and carbine. The fact that some prospective buyers might have served in the cavalry, giving them experience with the M1873 Carbine in .45-70, especially if their company commander had requested they be issued .45-70-405 ammo rather than the .45-55-405 carbine cartridge.