Have you noticed that the only foo parts out there are ones that can be popped in by the end user? If the mains and tiny fuse wire were so important, surely you’d want to also replace wire between the IEC and transformer, maybe the transformer itself, the power switch. But for most people this would require a repair person. So instead we mostly see fuses, cables, mains distribution b(ol)locks, mains regenerators, etc.
And then you have magic jumper cables for biwire speaker terminals (vs the wire inside the speaker). Hifi isolation furniture (trophy shelves) that are supposed to ‘open up’ solid state devices. Really? Sure, turntables, valves and phone stages... But treating your solid state equipment like The Princess and the Pea? Why not? It’s easy to install and looks cool(?), so it’s easier to sell than items that actually make a big difference but aren’t plug and play.