mohavesam, the engineers at Ruger use a jacketed bullet. And, as such,, if it works within specs for jacketed bullets,, it's "fine" with them. Cast bullets can be a whole different animal unto themselves. So,, to make them more accurate or especially to avoid leading,, chamber reaming has been a big benefit for the cast bullet shooter.
Cast bullets, when used properly,, follow the pattern of slugging the bore to determine the best diameter for the bore,, AND to measure the throats of each chamber to get a proper bullet to fit the firearm.
And if you really want to know if there is necessary work needed to make a gun shoot better,, start shooting at longer ranges than most would normally consider. Start at 50 yds & go out to 200 yds & see how accurate the gun REALLY is,, or if some tweaking might be necessary.
Too many folks feel that 5, 7, 10 or maybe 15 yds is the "correct" distance to judge how accurate a gun is. Well, I can tell you that real serious shooters usually begin testing a gun at 25 yds to get a base line & work out to longer distances to see how good a gun really is.
And for those who feel it's "magic" or "almost impossible" for a handgun to be used effectively at 100 or more yards,, all I can say is this; "Try your hand at handgun silhouette shooting,, where you have to knock over 50 lb (or so) steel rams at 200 meters." When you see it done,, you will be impressed,, especially when guys do it on a regular basis. That "game" proved that handguns can be very effective at long ranges,, AND that serious attention must be paid to being able to properly shoot a handgun for such accuracy.
So,, while you may feel that the engineers at Ruger are smarter than many average people,, (kitchen-table tinkerers,,, your words,) often they do NOT have the field experience NOR the trigger time MANY others who have serious knowledge about such a subject. Remember,, the engineers are there to build a product,, using normal common ammo, and make them rugged & reliable.
Or,, how about builders of the 1911 handguns? If they are so good,, then why are there MANY businesses out there to customize & make more accurate the proven 1911 handgun? Nobody disputes the genius of John Browning,, but as requirements required of the 1911 to do what shooters asked of it,, modifications abounded,, making the 1911 into a seriously accurate handgun. Wilson, Les Bauer, Jim Clark, and many others built a life long business making a good gun even better. Why dispute someone doing the same for a Ruger?