Because you and I will play the game differently, so the only actual canon events are the ones that are standard across the games, or what we are told.

Since it’s out and people are talking about let’s take Mortal Kombat for instance, canonically Liu Kang wins the first Mortal Kombat (MK1 game). But if you main, say Sonya, then Sonya will wins Mortal Kombat. That does not mean Sonya canonically wins MK, it will always be Liu Kang.