He also gets an exemption at home.
Probably it comes down to evening up the playing field so that you could get people on base more often. The BR is at a bit of a disadvantage in that he doesn't get any lead off, has a few feet extra to begin with (or has to turn around), and has to switch from thinking about hitting the ball to running in an instant. If you think about how many close plays you get at first given the current situation, think about how many baserunners you'd lose.