Pieter
The answer is very simple: BECAUSE THEY CAN NOT BUILT SUSPENSIONS.
Ever driven a Land Cruiser Prado off road? A land Cruiser pick-up off road or on tar? Ever driven a 70 or 80 series? They simply do not have suspensions in standard format. The LC Pick up is notorious for it terribly hard and unforgiving ride. A joke goes around that a kidney belt is supplied with every LC Pick up sold. The 70 series featured in Andre de Villiers'

never had a wheel on the ground, because the suspension has such bad articulation, that they had to install 3 diff locks on the car. It will be very interesting to see him drive without diff locks.
The Patrol's suspension is simple, efficient, durable and strong. The diffs are also much stronger than anything else on the market. Another thing, I don't know why anyone would buy a 70 series, because it's 1984 technology at 2009 prices...