For most of volleyball's first century, matches were scored under a side-out system: a team could only add to its score when it was serving, and winning a rally while receiving serve earned that team the right to serve next rather than an actual point. This made matches unpredictable in length — a set could theoretically run very long if neither side could hold serve — and made broadcasting the sport on a fixed television schedule difficult, since no one could say in advance how long a match would last.
The FIVB introduced rally point scoring in 1999, awarding a point on every single rally to whichever team won it, regardless of which team had served. The change was driven largely by the desire for more predictable match lengths and a faster, more continuously exciting product for television audiences and live spectators. Rally scoring was adopted alongside the introduction of the libero position around the same period, and together the two changes reshaped both the pace and the tactics of top-level volleyball.
Faster matches, higher stakes on every point
Under rally scoring, every single point carries direct weight on the match outcome, which raised the pressure on serving and passing — a missed serve or a shanked pass now costs a point immediately rather than merely surrendering the serve. Some lower levels and older recreational formats still occasionally use side-out scoring for casual play, but rally point scoring is now universal at every competitive and Olympic level of the sport.
A change that reshaped serving strategy too
Rally scoring also changed how coaches think about serving risk. Under the old side-out system, a missed serve only cost a team its turn to serve, not a point outright, which encouraged fairly conservative, safe serving. Under rally scoring, a missed serve hands the opponent a free point immediately, which — somewhat counterintuitively — actually pushed many teams toward more aggressive serving rather than less, on the theory that a serve tough enough to produce a meaningful chance of an ace or a bad pass is worth the increased risk of an occasional service error, since passive serving gives the opponent an easy first-ball situation every single time.

