A very good question, and so far as I know, completely unanswerable in terms of modern physics. We suspect it is akin to asking why do we experience the spin of the Earth ( day and night) differently than its mass. Time and space are 'just' two kinds of 'quantum numbers' that nature insists on using to keep track of what it is doing. It also needs to use spin and charge, which we 'experience' very differently than even time and space.