The seconds immediately after a foul are one of the few moments in a match when the defending team is guaranteed to be disorganized. Most attacking teams spend those seconds arguing.
What the defense is doing in those seconds
A foul usually occurs during a defensive action, which means defenders are moving toward the ball rather than toward their positions. The whistle finds them spread out.
Their instinct after the whistle is to walk back and re-form the block, and that reorganization takes several seconds. Until it completes, the shape has gaps that will not exist later.
The gaps are predictable. They sit in the space behind the defender who committed the foul and in the area the covering defenders were drawn toward.
The rules permit more than most teams use
A free kick may generally be taken as soon as the ball is stationary, without waiting for the referee, provided the referee has not indicated otherwise. Teams often forfeit this by handling the ball or by moving it.
Referees will insist on a formal restart when they intend to caution a player or when they have signaled for the wall to be set. Outside those cases the attacking team controls the timing.
The practical requirement is that a player is close enough to the ball to place it and play it immediately. That is a habit rather than a skill.
Why the appeal costs the advantage
The natural reaction to being fouled is to complain, and teammates often join. Every player facing the referee is a player not making a run.
By the time the protest ends, the defense has retreated and the restart is now against a set block. The team has traded a disorganized defense for a rehearsed one.
This is a coaching problem rather than a tactical one. It is fixed by rules about who touches the ball after a whistle and who looks upfield.
The receiver matters more than the taker
A quick free kick only works if someone is already moving into the vacated space. The pass has to have a destination before the ball is placed.
Teams that use this well assign that responsibility to specific players, usually the forwards nearest the ball. Their instruction is to check the defensive line rather than the referee.
Without that, the quick restart just gives the ball to a marked teammate under pressure. Speed alone is not an advantage.
When slowing down is correct
Not every free kick should be taken quickly. A restart in a dangerous crossing position is worth more with the box loaded, and a team protecting a lead gains from the pause.
The decision is about whether the disorganization in front of you is worth more than the delivery you would give up. That trade-off changes with field position.
Teams that make it consciously get value from both options. Teams that never consider it default to the slow restart and give the seconds away.