Beacuse if one side is leaking, the other is likely to leak soon, and/ or will be damaged in the course of the repair. New Holland recommends bushing replacement and it is often damaged in removal. The nature of the snap ring and its placement is such that it is cheaper to sacrifice it than spend $1.20 per minute (shop labor rate) to remove it intact for re-use. Your mileage may vary, and the economics of a DIY repair coupled with your tolerance for the odds of re-visiting the leak due to an incomplete repair may be different than that of a professional repair shop. I will tell you upfront that the spherical bushing is not cheap.