The tiebreak is a relatively recent addition to a very old scoring system. It solved a genuine operational problem and changed the character of a set in the process.
The problem of the open-ended set
Under the original rules a set continued until one player led by two games, so two strong servers could extend a set almost indefinitely.
Matches occasionally ran for hours beyond their expected length, which made scheduling unpredictable and left later matches starting in fading light.
Broadcast coverage made this worse rather than better, because a fixed transmission window cannot accommodate a match with no defined maximum length.
How the tiebreak resolves it
At a defined score the set switches to a short game decided by points rather than games, with service alternating so neither player holds a structural advantage.
The two-point winning margin is preserved, so the principle that a player must win clearly rather than narrowly survives inside the shorter format.
What changes is the ceiling. A set now has a knowable maximum length, which is what made reliable scheduling possible.
What it cost the sport
Long sets produced a particular kind of drama, where the accumulated pressure of repeated holds eventually broke one player's concentration.
Compressing that into a handful of points replaces a slow attritional contest with a short, volatile one where a single loose shot decides everything.
Purists argued that this rewards nerve over sustained quality, and the argument was never fully settled so much as overtaken by practical necessity.
Why final sets took longer to change
Many events retained an open-ended final set long after adopting the tiebreak elsewhere, on the reasoning that a match should be decided by play rather than by a short format.
Extremely long final sets eventually forced the issue, since they exhausted players to the point that the following round became meaningless.
Most competitions now use some form of tiebreak in the final set, though the point target and the trigger score still vary between them.
The effect on how players prepare
Because a tiebreak is a distinct format, players practise it separately, rehearsing serve patterns for specific point scores rather than treating it as ordinary play.
Return positioning also changes, since the reduced number of points makes a single break of serve within the tiebreak decisive.
Records of tiebreak performance are tracked closely for that reason, because a player who wins them consistently converts close sets at a rate his other numbers do not explain.
