Any utensil that is more than one piece uses something to join those pieces together, like a glue or rivets.
They also have seams, such as the wooden handles on a knife, where moisture and caustic detergent gets trapped. That attacks the glue or the metal of the rivets until it separates or corrodes.
Many knives that appear to be a single piece of metal aren’t; the blade may be stainless steel, but often the handle is hollow and again, joined to the blade with some kind of cement.
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