The moon clips were adopted to make loading and unloading faster--it's sort of like a "round magazine."  Six rounds load at once, six rounds eject at once.  The clips were not absolutely necessary with the Smith because they were made with shoulders in the cylinder to headspace the cartridges, and you could fire them safely without the clips--but you'd then need something like a pencil to eject the empties.  Colts did require the clips as they were bored straight through without headspacing shoulders.  Firing them with clips could result in them slipping down the cylinder without the firing pin striking the primer hard enough to set it off.  Colt changed this in later guns and made their cylinders with headspacing shoulders like S&W, but both of the revolvers, Colt & S&W, were a LOT faster to use with moon clips.  And even though a rimmed round like the .45 Colt would have ejected quickly, loading would have been much slower--one at a time vs simply dropping a loaded clip into an open cylider.  And nobody wanted to introduce another cartridge into the supply chain.

These military revolvers, both known as the M1917, were popular, and S&W sold a lot of them to civilians in the interwar years.  The military guns had been made in large numbers and were brought out of storage in WWII and were reissued to plant guards, rear echelon troops, and others.

By the time we'd fought two wars with moon-clipped, .45ACP revolvers, Americans were used to them and want to buy them.  Smith & Wesson continued to upgrade their models with the Model of 1950, 1955, Model 25, and by the late eighties the Model 625 came out.  It was, if I remember correctly, the last of the .45ACP revolvers.