Trackrod ends

Can anybody tell me why the height of the trackrod ends, going into the hub, is adjustable??

Haven't looked at mine, but is it to reduce bump steer if you lower the suspension?

I can't see how this would lower the suspension.
Surely the hub height is set by the springs and wishbones??

No what I mean is that if you were to lower the suspension... shorter springs or coil overs, then you need to adjust the height of the steering tie rod arm to prevent bump steer occuring.
(So the tie rod stays at the same level it would do if at the original height)