Here's why:
* We haven't found every exoplanet: We've only discovered a tiny fraction of the exoplanets that likely exist in our galaxy.
* Distance is constantly changing: Stars and planets are constantly moving, so the distance between them is constantly shifting.
We can identify exoplanets with the greatest known distances, but these distances are constantly being updated as new discoveries are made.
If you're interested in the exoplanets with the largest known distances, I recommend checking out online databases like the NASA Exoplanet Archive or the European Space Agency's exoplanet catalog.