Safety is a design issue

SO FAR I have been very, very happy with my 2006 Ford Territory Turbo, but I became aware of the balljoint/control arm issue only when the car went in for its routine 75,000km service. I was stunned at what needed to be done. I am also lucky that my car has had all of this rectified under warranty this week, but I am wondering why all of this was required after my car has done only 76,000km and has never been off-road. My dealer has been fantastic about it, but said to me only that there had been a revision of the bushes and balljoints and this then ``should fix'' the problem. However, it sounds more like an inherent design issue than a material issue, and one that will probably recur. Can you shed any light on this?