In the past (barbaric times) it was common for disagreements between individuals, nations, and worlds to be solved by having the life forms on both sides kill each other. These brutal conflicts resulted in countless lives being lost and billions of credits worth of resources being wasted. An untold number of species have been removed from the galaxy due to this type of behavior.
If one of these hostile species had a high enough technology they often created robots that could be used to fight in their place. This saved lives on the side that owned robots but increased the loss of life for those who did not. If both planets were advanced enough they would both use robots to fight each other. This greatly reduced the loss of life on both sides but the damage to the surrounding environment and economy was just as great.
This went on for many cycles until eventually the Galactic Trade & Warfare Organization, which at that time was known only as the Galactic Trade Organization, decided that the loss of resources in these conflicts was adversely effecting the galactic economy. They imposed strict rules and guidelines on how conflict could be handled. Under the new rules both side would enter into an agreement in which each side would create one robot that would compete against a single robot created by the other side. The fight would take place in a specially sanctioned arena on a neutral world. The winner of the fight would win whatever was agreed on and the loser was allowed a temporary immunity to any conflict.
This solution became extremely popular among the ‘civilized’ planets (planets refusing to solve their conflicts in this manner are considered ‘dangerous’ and are quarantined from the rest of the galaxy). Once the Galactic Net (GNet) was instituted, live feeds from robot matches quickly became the second most viewed material on it (right after "mating rituals"). With on-site betting, tourism, and ticket sales, hosting a match on your planet was a great source of income. The matches became so popular that many planets would ‘make up’ disagreements with each other just to create a match to broadcast. To reduce the number of made up conflicts, the Galactic Trade & Warfare Organization started a special ‘training branch’ of robot conflict, thus the Robotic Combat League was created and Robot Combat became an official sporting event.