There is one shot in Star Wars: A New Hope where one Tusken Raider, from a high cliff on a rock mesa, aims at Luke's speeder that zips through a canyon below; then, a second Tusken Raider touches the sniper from behind and, after a brief argument in their barbaric tongue, seems to get in the final word and the nomads scurry over the rocky terrain.
The fact that Tusken Riders shoot down a fast racer during the Boonta Eve Classic in 32 BBY demonstrated that these sand people are skilled marksmen, thus, why, having a good overlooking from a high position, they didn't shoot down Luke's X-34 with their long ominous laser rifle?
Here a picture of the miniature land speeder used (via chroma keying) for the shot mentioned in my question. I wanted to show this picture that shows (imho) the meaningfulness of this brief shot.
It is interesting to note what the Star Wars - A New Hope 4th revised script tells about the shot.
One of the marginally human creatures raises a long ominous laser rifle and points it at the speeder but the second creature grabs the gun before it can be fired.
Thus, the second Tusken Raider didn’t touch the shoulder of his pal but grasped the gun before shooting.