Grey is a popular color. It always has been and it always will be because for interior designers, it's such a great neutral color.
Stone Grey provides many shades of grey and will fit in with many, many other decorative possibilities. And the room's deep-thinking and/or shy occupants have something to enjoy as they direct their gaze downward.
You can also see where the rug's designers have used the "erased technique," a deliberate effort to give the impression of natural wear.