When someone respected and well known dies we consider their final words to be important and significant, even a distillation of that person's wisdom throughout their life. The most important last words ever spoken were spoken by Jesus to the disciples who were to be his witnesses, taking the gospel to the whole world.
Of course, Jesus' teaching and example investigated here are not strictly his very last words but his meeting in the upper room was the last time he saw his disciples together before he was arrested and put to death.
The wonder is that Jesus knew exactly what was going to happen and so carefully prepared his church for what was going to come. Although we are separated by two thousand years from this event, there is a real sense in which we are also in that room, listening to the saviour and able to learn so much from these last words to his disciples.