Different times, metallurgy, and designs. Today, there are loads that Rugers can handle that ammo manufacturers and reloading publications explicitly state are exclusively for certain Ruger revolvers.
The design differences of S&W vs Ruger matters more to which is stronger and more durable than the type of metal used. Both S&W forged and Ruger cases frames can withstand the pressures of .357 and even 44 MAG. Heck, Buffalo Bore sells 44 MAG +P+ ammo that's only recommended in Ruger, Taurus, Colt, and Dan Wesson revolvers, but no S&W revolvers. There are 45 Colt loads that are only for Ruger revolvers as well. Everyone seems to have this misplaced hyperfocused obsession with the type of steel S&W and Ruger uses, when it's the differences in how they are designed that basically makes one stronger than the other depending on the model.