At one time S&W and Colt both used built in spacer pads to keep the hammer and trigger centered; that prevented rub marks on those parts. The pads were hand adjusted with a file during assembly. But all that added to the cost of the gun, and the "problem" was purely cosmetic, so those have been eliminated.
One thing that can help, though, and cost less than shims, is to remove the sideplate and stone it to remove any burrs at the edges and do the same with the edges of the frame on the other side. With the Ruger, both sides of the frame have to be stoned.
Of course, shims do no harm but be very careful not to use shims that are too thick without either removing some frame/sideplate metal to compensate or thinning the shim. If the shims are too thick, the result can be a warped sideplate and binding of the hammer and/or trigger.
Jim