Nature doesn't literally "preslice" oranges, but the way oranges are structured can make them easier to separate into segments. Oranges are made up of individual sections called carpels, which are filled with juice sacs. This natural segmentation allows for easy separation when you peel or break apart the fruit.

The design of oranges and other citrus fruits is an evolutionary adaptation that helps with seed dispersal. When animals eat the fruit, they often discard the seeds, allowing new plants to grow in different locations. The juicy segments also attract animals, ensuring that the fruit is consumed and the seeds are spread.

I had to search 😢

Nature didn't do shit.

Sure, maybe the original mandarins, pomelos, citrons, papedas, and possibly kumquats (there's also Buddha's hand, but we don't talk about Buddha's hand) were sort of pre-sliced, to help with seed dispersal, but like with practically every fruit and vegetable we eat we took that small, dry, bitter crap and started selecting for larger, juicier, tastier, and easier to eat.

And then we went, nah, that ain't it yet... and we started grafting (because apparently plants are kind of ok with us playing Frankenstein with them while they're still alive, or at least we can't hear them complain, and probably wouldn't care if we could).

We made oranges, and most of the citruses we eat.

Why do oranges come pre-sliced..? Because we made it so.