What is the purpose of the troop occupying a tile when you cannot use them to join in a raid?

For giving away kill points or as placeholders so nothing spawns in its place. Example player A wants to keep his/her/it's reserved spot and asks player B to put an encampment on it. Time passes, player A wants to come back and asks player B to recall or if from another faction and arranged like that player A asks a random other player to attack encampment and instantly recall after hit to clear the spot. Or they can hit it themselves risking in the time of their troops returning that something spawns in its place anyway