You can pick up a carpet and move it somewhere else. It's a unique thing of a certain length and width. It has finished edges.
In the second picture, which we call wall-to wall carpeting, at least in the U.S., it has no predetermined shape, it's cut to fit the shape of the room, it doesn't have finished edges, it's attached to the floor and can't be moved. It's not a thing, it's a material - like tile or wood. You don't say a wood either. You can say a tile about one tile, but not when it covers the whole floor. It's just tile. It's just wood. It's just carpet.