Why is the Land Rover Defender so down on power??

I understand that it was never built to break any land speed records, and most people who will actually use a defender probably wont need to go faster than 60 mph at the most (95 Km/h). But the thing is just so damn heavy you'd expect them to give it something with a little more horsepower and an extra 50 to 100 ftlbs of torque.Why is the Land Rover Defender so down on power??
Greater displacement often equals greater fuel consumption. Try getting out and trudging to the nearest BP station when you are in the middle of the Serengeti.