There was a time when a game was played for the love of the game. The rules of an established game were respected and traditionally followed. But now they are changing with the commercialization of sports. The rules and the game itself are changing according to the demands and tastes of the spectators. One of the reasons is that only viewership will bring in revenue and sponsors (more revenue). One of the best examples is cricket.
Traditionally (test) cricket was played across five days. A tradition was followed meticulously by all cricket-playing nations. Nowadays, spectators do not have the time (and option) to stay away from work for five days to watch a game. Then the one-day format (limited over) developed and became hugely popular. Even world cup tournaments are now being held. The next development is the 20:20 format, whereby the game will be over within half a day. This now resembles the professional club format in other sports like soccer, baseball, and basketball.
A threat that the five-day game will disappear also exists. The transformation from a six-player game to a two-player game in the case of volleyball is another example. The beach volleyball where two players wearing bikinis/briefs has even become an Olympic event. Spectators need innovation and variation. The invention of headball (a variation of volleyball) and handball (a variation of volleyball) are examples. All these sports events now have professional leagues, associations, and teams.