Every match contains several kick-offs, each one a moment where a team has uncontested possession and knows exactly where all twenty-two players are standing. Very few teams treat that as an opportunity.
The starting positions are fixed and known
At a kick-off the opposition must be in its own half and outside the centre circle. No other restart guarantees the defending team's shape in advance.
That means a routine can be designed against a known arrangement, rather than against whatever formation the opponent happens to have recovered into.
It is the closest football gets to a play from a static position with full information, which is why the neglect of it is slightly odd.
The two conventional options are opposites
The common approach is to play the ball backwards and begin a controlled build-up, treating the kick-off as an ordinary possession with a guaranteed clean start.
The alternative is to play long immediately into a corner or towards a target, accepting the loss of possession in exchange for territory and a throw-in deep in the opponent's half.
Both are defensible. The choice usually reflects whether a team believes it wins more from the ball or from field position, which is the same judgement that governs their goal kicks.
The long kick-off is a pressing trigger in disguise
A ball played immediately into the opposition corner forces a defender to deal with it while facing his own goal, with the whole pressing team advancing behind it.
Because the pressing side chose the moment, it can be perfectly organised as the ball arrives, which is rarely true of a press initiated in open play.
The outcome sought is not possession from the header but a throw-in, a rushed clearance, or a mistake in a dangerous area within the opening seconds.
Restarts after conceding are a different problem
A kick-off following a conceded goal happens with a team that has just been hurt and an opponent whose concentration frequently drops in celebration.
Goals scored shortly after a restart are common enough that many coaches deliberately slow the game at that moment, taking time to reset positions and instructions.
The team that conceded faces the opposite temptation, wanting to respond immediately, which is often when a second goal gets conceded rather than one scored.
Why rehearsal is still rare
Training time is finite, and a coach weighing kick-off routines against corners will reasonably choose corners, which occur more often and generate more goals.
There is also a reputational asymmetry. A designed kick-off that fails immediately looks foolish in a way that a failed corner does not, because the whole stadium is watching a restart nobody expected anything from.
Teams that do rehearse it tend to use one variation sparingly, keeping it for occasions where an early moment of territory or disruption is worth more than the usual controlled start.