Let's say you wanted to move your soldiers to a certain spot on the map that is so far away, it will take several turns to reach it. So, on each turn, for each soldier, you'll have to:
1.) Select the soldier
2.) Scroll the map all the way to the target location
3.) Double-click the tile you want to move into
... which gets pretty tedious on larger squads. Now, what if the game actually remembered which tile a soldier was trying to move into before he ran out of TUs and you could re-issue the same movement order by simply pressing a hotkey? You would only have to issue the movement orders once and then just keep pressing the hotkey on each soldier until everyone has reached the target location.
Jagged Alliance 2 had a feature similar to this and I thought it was really handy