Goalkeepers facing penalties increasingly stay upright until the last possible instant rather than committing to a side. The shift is a rational response to changes in how penalties are taken and officiated.
Waiting buys information
A keeper who dives early is guessing, and a guess is right roughly half the time regardless of how good the keeper is.
Delaying allows him to read the taker's standing foot, hip angle and the shape of the striking leg, all of which give away direction.
Those cues appear extremely late, which is why the technique requires an explosive push rather than a long dive.
Takers stopped shooting into the corners
Against keepers who dived early, the safest penalty was a firm shot into a corner, since the keeper had already committed.
As keepers began waiting, more takers started aiming for the middle or for a height the keeper cannot reach even when he reads it correctly.
That in turn rewards a keeper who stays on his feet longer, and the two adaptations have pushed each other in the same direction.
The line rule constrains the movement
A goalkeeper must have at least part of one foot on or above the line when the kick is struck, which limits how much he can advance beforehand.
Video review made this enforceable in a way it had not been, since a still frame settles what the naked eye could not.
The result is a keeper who cannot narrow the angle by stepping forward, so his only remaining advantage is timing.
Movement along the line replaced movement forward
Keepers now shuffle sideways, raise their arms, and use the permitted lateral movement to occupy attention without breaking the line rule.
The aim is to make the goal look smaller and to disturb a taker's rhythm during the run-up rather than to reach the ball sooner.
Some of this is theatre, and some of it genuinely affects a taker who has decided to place his kick precisely.
Why it is not universal
Waiting requires exceptional reaction speed and leg strength, and a keeper who lacks either will reach neither corner from a standing position.
Some keepers therefore still commit deliberately, working from research on a taker's habits rather than from a read of the run-up.
Both approaches are defensible, and the choice reveals whether a keeper trusts his information about the player or his own reactions.