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Shared ground path vs shared supply path

Hi. I am just getting into PCB design and I consistently see recommendations to never share return paths between signals. It seems this is to avoid noise due to the shared impedance of the return path. What I understand from this is to ensure that each signal has its own path trace/via/plane to ground. However, I have never seen any mention of sharing or splitting the power path (supply path?). Examples will just show 1 or 2 longer traces that branch out as they go, at various points along the board to supply power to components. Surely the shared supply path would introduce this same noise that a shared ground path would? Why is it so important to separate the ground paths, but when it comes to power, just do whatever? Perhaps I am misinterpreting the guidelines.