I grew up with non-stainless knives and the stains that developed on the blades. We didn't call it "patina", we called it stains or "crud". As a kid, we used to clean the stuff off our knives by sticking them in the ground a few times. The abrasion removed some of the stains and made the knives shine a little bit. Then a few swipes on an Arkansas stone would get it fairly sharp and ready to use. Since it was hot and humid where I lived, knives would rust fast if you didn't clean and oil them, patina or not. Lots of nice pocket knives and sheath knives got tossed in the trash due to having been put away dirty and/or damp for a few days, weeks or months. Back then, knives were pretty cheap so it was no big deal to most folks. You could buy a decent sheath knife for a dollar or two that would get you through the hunting season. Frequently used pocket knives that were carefully cared for to prevent rusting had to be kept sharpened and that used up the soft steel blade relatively fast. So knives were considered disposable. Most people looked on the patina as inevitable evidence of the knife deteriorating with use and time.
Fast forward to today. Various stainless steels are available and have proven to perform superbly. For most jobs, it simply works better than the old carbon steels of the past. But patina is suddenly trendy with knife enthusiasts. Instead of it forming naturally with use, knife people today affect a patina with various methods. Seems a bit odd to me--all you gotta do is use the knife and it will stain. Makes me think a lot of people don't really use their knives much. Which is okay with me since I have a lot of knives I don't use either. And, no, I'm not putting down traditional carbon steel knives. I love those knives and own a bunch of them. My favorite knife today is the Spyderco Gayle Bradley and it's made with M4 steel, a carbon steel that resists corrosion well. However...for practical purposes, I also frequently carry stainless knives with shiny, scratched blades.
WD-40. The stuff must be the most disparaged and most used oil in the world. While there are lots of things I wouldn't use it for, it does help to prevent corrosion and it does clean knives. As an example, I have an old Kabar USMC knife and a Camillus-made Becker BK9 I use in the backyard for various jobs. Both are stored in their sheaths, something we're told not to do. After using them, many times I just quickly wipe them off and spray them with WD-40 before putting them away. They are stored in an outdoor cabinet under a shed in the backyard...the Kabar has been kept there over 20 years, the Becker at least 10 years. They don't look like new but they haven't rusted away either.