Deciding sets in the major tournaments now end in a tiebreak rather than continuing until someone leads by two games. The change was made for reasons that are mostly logistical.
An advantage set has no upper bound
Under the older rule, a set continued until one player led by two games. On a fast surface where serve dominates, that condition can go unmet for a very long time.
Matches of extreme length are rare, but they are not distributed randomly. They occur on surfaces and between players where holding serve is easiest, which is exactly where the format is most exposed.
Because the ceiling is unbounded, no schedule can be constructed that accommodates the worst case, which forces everything after it to move.
The scheduling cost cascades through a draw
A tournament runs matches sequentially on a limited number of courts. One match overrunning by hours pushes every subsequent match on that court back or into the following day.
Broadcast windows, ticketed sessions and curfews all fail together, and the players displaced had no involvement in the match that caused it.
The knock-on effects reach into later rounds, since a player who finished at midnight may be scheduled again earlier than an opponent who finished in the afternoon.
Recovery time is a competitive variable
An extremely long match imposes a physical cost that persists for days. A player who survives one frequently loses the next round heavily, having won a contest that removed him from the tournament in effect.
That outcome is unsatisfactory on its own terms. A format that rewards the winner with an insurmountable disadvantage is not measuring what it intends to.
Tiebreaks cap the exposure, so the physical cost of a close deciding set stays within a range the following round can absorb.
The tiebreak preserves the requirement to win clearly
A tiebreak still demands a two-point margin, so it does not replace a clear win with a coin toss. It bounds the length while keeping the principle.
Serving order rotates so that neither player benefits from the side they began on, and the change of ends partway through addresses conditions such as sun and wind.
The result is a short, high-pressure sequence that concentrates the set into a handful of points rather than dissolving it into attrition.
Different tournaments settled on different triggers
The majors did not adopt an identical rule at the same time. Some began the deciding tiebreak at a later game score, and some used a longer tiebreak requiring more points to win.
Those variations were attempts to preserve some of the drama of a long deciding set while capping the extreme, and they produced inconsistency between events.
Convergence on a common rule came later, driven by players and officials who wanted the same conditions at every major rather than four separate endgames.
