IMHO, the use of lube depends greatly upon the use of the firearm. On the more recent S&W products incorporating MIM parts, you will find the wear surfaces to be very smooth, requiring very little if any lube. On older guns with machined parts, this is not the case unless someone took the time to stone the surfaces smooth.
Steel on steel contact, especially in rubbing form instead of simple push against contact, causes friction, even for smooth parts. But it's the amount of friction that is important. The surfaces of an engine's crankshaft for example would be in contact with a bearing surface for anything from 600 RPM to 6000 RPM, which would produce incredible friction, especially when one considers the lateral forces pushing against it by the pistons, were it not for the oil film provided by the engine's motor oil. We tend to carry this necessity over to all things metallic, when in fact it is not necessary and can even be detrimental. The internal parts of your revolver will never experience the wear forces an internal combustion experiences in one minute over the entire lifetime of the revolver, unless perhaps you shoot competition weekly, in which case, I'll extend that to 2 minutes tops.
If you take the side plate off your S&W and use a light coating of a thin oil such as Rem Oil, you will likely never have a problem, provided you periodically repeat the process, properly cleaning the old oil and accumulated grunge with it. Oil traps and holds any particles it comes in contact with, including dirt, sand, skin cells, dust and most importantly, byproducts of the powder combustion process. The interior of these revolvers isn't sealed, and 'stuff' will get inside. Lack of oil allows these contaminants to fall away to the lowest part (thanks to gravity), which can keep them away from the most important moving parts, the hammer and trigger pivot points and sear engagement areas.
Using some lubricants can actually cause a firearm to fail. Heavy oil (think motor oil here) and "gun" grease can become sludge or even act like glue on a cold winter morning. That's why I use nothing but Rem oil on my revolvers. Yes, you read that right, I use oil, as I'm old school. But as cited above, I disassemble and clean religiously thus avoiding the build up of dirt in my firearms.
So to the basic question: is it needed? Nope, not according to the factory nor logic of the new types of parts used. Will that stop old guys like me who grew up with parts made under different conditions and who were told metal against metal is always bad? Nope again. So OP, it's up to you to decide for yourself.
