Because it is true. That you have a body, but in three dimensions, and they are at right angles to each other, and, centering on your body, they are coupled. Because I made it that way. Centered on points. Take gravity, for example.
Gravity draws time and space together.
And not only in the way that Einstein intended, meaning the curvature or bending of space. But, rather, even in a Euclidean sense, gravity defines the relationship between time and space centering on mass. It is force. Even without Einstein. That is, even without relativity, or relativistic deformations.