It lets them get more trail, for stability, without using lots of rake, which helps avoid front wheel "flop" in low speed turns. HD tourers have had it since the first shovelhead engined rubberglide tourers of about 1984 (can't remember the alphabet soup model designation).
1600cc Kawasaki Nomads had the same, not sure about the current generation.
If you check really closely, you will see that the steering stem and the fork tubes aren't parallel.
High speed stability, with responsive, easy lowspeed turn control, that describes X bikes handling characteristics perfectly.
It can present styling challenges, because the steering head has to be a long way forward of the fuel tank, to allow the fork tubes room to drop back in tight lock very low speed turns, but this is only apparent in naked bikes, so Cross Roads and HardBalls, rather than Cross Countries, Road Kings rather than Street Glides.
2013 Hard Ball
Stage 1 mufflers
K&N air filter
Rubber air dam removed
Whole lot of extra cable ties, shrinkwrap and tape on loom
Hard chrome spherical joints in back
Hammer front guard
Wide Glide fork boots