In soccer, why do multiple offensive players often stand near the ball during a direct free kick, when only one of them is going to end up taking it?
Tactically, wouldn't it benefit the attacking team to put more numbers near the goal box in order to, say, collect a rebound?
Having multiple players by the ball can allow for more offensive opportunities. It doesn't mean that it will create better chances, but if played correctly, having 2 or maybe 3 players behind the ball allows for having more opportunities to score.
Right footed players's crosses and shots naturally curve to the right and back in, and the opposite is true for the left footed players. Now consider having a free kick. having players of opposite dominant foot allows for both curves. It leaves the goalie with less information on how the shot or the cross would travel if there was only one player behind the ball. The defenders also can't prepare with certainty either.
By having multiple players behind the balls you can draw up plays you simply couldn't otherwise.
One of those plays is for the free kick taker to pass the ball to another player behind the ball, and have them take the shot or pass it back for the taker for a shot. This is done when there is not enough space for a shot, by making a pass (although a short one) more space is created and it becomes easier to clear the ball around the opponent's wall. A good and recent example of such play is Tony Kroos's goal game winning goal for Germany against Sweden in the group round of the 2018 World Cup. The free kick spot was far too much on the left and almost impossible to score from. But a small pass of about 4 or 5 feet was enough for Kroos to bend the ball by the defenders and score a goal.
Another possibility is that you can have players fake taking a shot which can make the defenders and the goalie move to the wrong direction, opening up space for another player to immediately take the shot after him.
Similarly you can have one of the player behind the ball go for a run. Defenders can't mark players behind the ball as they have to be 10 yards behind the ball, this is was the wall is formed. So one of the players behind the ball can run away and find himself in some open space for a better option.
Additionally, you can't directly score from all free kicks in soccer. Some kicks are indirect, meaning that if you kick it straight in the net, the goal wouldn't count. In this case passing the ball to another player behind the ball or crossing it for other teammates is necessary.
Tactically, it provides choices.
The defenders will set up in particular areas in and around the box, leaving others more open. Attackers in those open areas are more likely to be free.
Added to this is the effect of drawing runners. When an attacker begins to lead in one direction, the defender marking them will follow, changing the exact location of the open areas and who the free attackers are. Depending on the runs made, a different angle or curl on the free kick may be needed.
On the other hand, if the defenders are marking zonal, the attacking leads can be made to one particular area and create an overload there. With more attackers per defender, the odds that an attacker touches it onto goal or plays it to another free attacker go up.
Finally, if it is a direct free kick, and the team has a player with strength in taking long free kicks, the added threat of this player makes the goalkeeper's job that much more difficult: is it going direct or to another attacker, and where? Having a second kicker multiplies the number of threats on goal and increases the odds of scoring from the kick. Note that even if the free kick is indirect, a second kicker can take a shot from a very small pass by the first kicker, creating the opportunity where a single kicker could not legally score.
