No matter how well you know a recipe or how exacting your measurements, the environment can influence the outcome of what you bake.
Take, for example, the loaves of bread I made about a week back: I made two batches at the same time, with the same ingredients of the same amounts, let them rest in the same bowls in the same location, and baked them both at once in the same oven.
One came out with more texture upon it than the other, and the other was slightly less dense.
In baking, the conditions in the environment -- humidity, temperature, etc. -- can make the outcome of what you're making a surprise. You can have a general idea of what the results would look like... but you can never be certain. No matter how intimately familiar you are with the recipe or how precisely you measure the ingredients, you can't really control the environmental factors that influence your baking. To an extent, perhaps, but not totally.
Or, instead of baking, take Dungeons & Dragons. The Soulborn Engine is the Dungeon Master, and no matter how well-versed we might be in the lore of the world, we're playing alongside other players and rolling the same dice. The human element, coupled with the lack of loaded die, ensure that no matter the meta-knowledge or how exactly you follow in your footsteps of the last run, you can't get the exact same story.
So, to answer your question about the 'magic' of being a player -- I think we'll be just fine :)
