Why has the family feud lasted three generations and why don't Ulrich and Georg just shoot each other?

The feud between the Gradwitz family and the Znaeym family has continued for three generations because the Znaeym family has never recognized the Court's judgment to remove them from the Gradwitz land. The Znaeym family has continued to hunt and otherwise trespass on the land. In the current generation, the feud has become more personal and potentially violent.

Ulrich and Georg do not shoot each other when they meet for a few reasons. First, they meet face to face and probably do not have enough time and/or distance to raise a weapon without the thwarting the attempt or mirroring it. Also, both men have been raised to be courteous, even if not warmly; manners prevent one man from harming another after meeting in such close proximity. Finally, before either can act, a tree pins both of them to the ground, giving no time for personal interaction before trapping them.