Lockouts are freewheeling hubs...
They disconnect the front wheels from the front transmission, as even when you select 2WD in a 4WD vehicle you are still pushing the front halfshafts, diff and prop shaft round up to the transfer box (in a standard 4x4 setup) which can produce quite a bit of drag.
Lockouts/freewheeleing hubs stop this happening and can help with tyre wear and fuel consumption
It may be a tracking caster camber issue thats highlighting the tendancy though