Because we have sampled all states of the hypothetical quarter, and are constricting many, many values concerned with flipping.

The same can't be said for the atoms in the sun.

We have complete, verified descriptions of what the possible states look like. You can predict precisely how long it will take a cannonball to fall to the ground (at least in a vacuum), even if you've never dropped it from exactly that particular height before.

"Precise" - to within some tolerance. At some point you reach the uncertainty limits allowed by quantum mechanics.

You also have to make an arbitrary decision about when the cannonball touches the ground. How much interaction is needed between the atoms of the cannonball and ground before you say there's contact?

These issues don't exist in the GoL universe.