Plating processes were about rust prevention. Going thru the steps means alot of degreasing, and if the final goal is a bright reflective chrome it also takes a lot of expensive hand polishing and buffing between coats. Done poorly the lines and edges of a firearm get blurred.
Lots of older knives were done that way and many imports got the treatment, too. Since the edge was ground and finished to bare metal the contrast between carbon steel and nickel plate would be night and day. That edge would also allow entry under the plating for corrosion. It was still better than no plating at all, and for the better grades of knives preferred. A lot of presentation blades got the treatment, as did ceremonial swords and holiday carving sets.
Once stainless could be done in equivalent metals or at least affordably the change came around, the '60s saw the introduction. We were already used to the look, better grade guns were doing it, so a stainless slide with matte finish looked like electroless nickel. For most intents and purposes of the gun owner it performed about the same in resisting corrosion. When the EPA started cracking down on requirements for plating then stainless got a big boost in replacing the look. Auto makers went to vacuum plated aluminum for trim and that was the look of the '80s in cars and guns. Big honking stainless auto pistols and aluminum bumpers on the economy cars because gas was so expensive - up to $1.65 a gallon. Yuuuge price increase.
The guns are collectible, the cars, not so much. Plating died in that era as the haz mat costs were too high. In knives stainless was the practical and commodity choice. Solingen still made plated blades but they were long out of style. Gunmakers didn't offer the finish much and the few smiths that did plate charged accordingly. Still do.
While stainless does literally mean that it will stain less than carbon steel, it can be restored to it's original finish with inexpensive use of the proper abrasives - grit pads or bead blasting. Nickel, however, requires stripping, the affected area cleaned up, which could create ripples in the finish, and replating. Gets complicated and expensive.
