The paper wrapping and spacers withstand this movement when your transformer is new. As your transformer ages, it loses this ability. Beyond this point your transformer may not reliably withstand the next surge load or short circuit. All the metal and paper aren't sitting alone inside your transformer. When the oil is not providing one of these functions, servicing will be required to assure Maximum Transformer Life.
Oil is an organic compound.
Oxidation and decaying products destroy the paper in your transformer. These bad actors form in your transformer from oxidizing oil, then take up residence in your paper insulation. If allowed to continue unchecked, oil decay products will form sludge deposits in your transformer. Accelerate destruction of paper insulation. Eventually bridge the dielectric gap at some point and cause flashover and failure.