Grit in the pile, soil in the joints
Floors take the most abuse in any building and show it last. Carpet fibers pack with grit that cuts the pile from the inside, so a gray path forms down a hallway long before anyone notices. Grout is porous, so mop water carries soil into the joints and leaves them darker than the tile around them.
Finishes suffer too. Old wax builds up in layers and yellows at the edges of a lobby. Hardwood loses its sheen where grit grinds under foot traffic, and bare concrete holds stains that set harder the longer they sit. A tired floor makes the whole room feel tired, and it is the first thing a client sees when they walk in.