It has to do with the consolidation of the front axle/hub assembly
No longer does the OEMs make their own and outsourced to become an assembly
So reduced cost is the main goal, IMHO
Since all one assembly, they removed the half axle to hub gear that was the
component 4x4 'hubs' employed to engage/disengage.
The half shaft is now constantly driven by the tires/pavement movement and the
dis-engagement is managed inside the front diff pumpkin