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It has to do with not using them.

Procedural edge-related dirt/wear is object specific, it's not something that can be tiled like bricks or floortiles or decking, so it is kinda moot, isn't it? Anyway, it sounds like the dirt shader is slow, not the tiled textures, so why not just bake the dirt/wear map and apply it over the tiled main texture? Dirt maps seldom need to be high resolution.