Grass shortens the point and lengthens the decision

What the surface actually does to the ball

Grass is slick and the blades do not grip the ball, so a delivery that lands on it retains more of its forward speed than on any other regular surface. The bounce is also lower, because less energy is converted from horizontal to vertical movement when the ball skids rather than bites. The combined effect is a ball that arrives sooner and at a height below the zone most players prefer for their groundstrokes.

Spin has less effect than elsewhere, since the surface does not grip enough to convert rotation into a dramatic change of direction after the bounce. Those are the physical facts, and almost every tactical feature of grass-court play follows from them rather than from tradition.

Why the first strike is worth more

When the ball arrives quickly and stays low, a defensive player has less time to recover position and less height with which to generate his own reply. That makes it much harder to construct a long rally, because each shot is more likely to end the point than to continue it. The consequence is that the serve and the shot after it carry a disproportionate share of the outcome compared with slower surfaces.

Players who rely on wearing an opponent down through movement find the mechanism unavailable, since points end before the accumulation has any effect. This is why grass rewards players whose game has a clear first strike, even when their overall consistency is lower than their opponents'.

Shorter preparation rather than faster swings

The instinctive response to less time is to swing faster, which reduces control and does not actually solve the problem. The effective adjustment is to shorten the backswing, so the racquet has less distance to travel and can arrive on time without being rushed. A compact take-back also keeps the racquet face more stable through contact, which matters on a ball skidding low and arriving with pace.

Players who make this adjustment appear to be hitting more softly and are in fact meeting the ball earlier and cleaner. Those who do not tend to be late on the forehand in particular, since the larger swing on that side has further to travel.

Getting lower and staying there

A low bounce means contact happens closer to the ground, and the only way to strike it well is to lower the whole body rather than to reach down with the arms. That requires bending at the knees and hips and holding the position through the shot, which is physically demanding across a long match. Players who lower only their racquet end up with the arms below the shoulders and no ability to drive through the ball.

The habit is trained specifically during grass preparation, because it is not required to the same degree on other surfaces. It also affects recovery, since rising between shots costs time that a fast surface does not provide.

Deciding earlier than feels comfortable

Because the ball arrives sooner, the decision about what shot to hit has to be made further in advance of contact than on a slower court. That means reading the opponent's contact and the ball's early flight rather than waiting to see how it behaves off the surface. Players who wait find themselves choosing a shot while the ball is already on them, which produces the late, blocked reply that grass punishes.

The compensating advantage is that the low skidding bounce is predictable, since the ball does not deviate much once it has landed. So the early decision is safer here than it would be on a surface where the bounce introduces genuine uncertainty.