OK, if you have EVER been printed, then you are in the database.
But that data is subdivided into many categories. There are arsonists, murders, kidnappers, organized crime members and many other sections of the database.
This is simply for faster searching. If you have a latent print at an arson scene, it would be faster to search the arsonists section FIRST, then if you do not get a match, only then do you bother searching the rest of the database.
If every search searched the entire database, all seaches would slow to a crawl and the queue to do a search would be unbearable.