A stainless steel folding knife isn’t 100% steel. In fact, it has about 12% chromium added to it, for two specific purposes. These are to reduce corrosion and rust. The take away is that the steel becomes slightly softer. Stainless steel is also recyclable, for those who are earth conscious. Quite possibly the biggest draw for many is the look of the stainless steel. It has a spotless appearance and makes it much easier to spot any staining or rust so it can be cleaned right away.
Source: https://www.xhunter.com.au/hunting/blades/knives/pocket/