Parables teach a lesson. Unproductive branches are pruned and burned.
John 15:6
[Men gather them]The word "men" is not in the original, and should not have been in the translation. The Greek is "they gather them," a form of expression denoting simply they are gathered, without specifying by whom it is done. From Matthew 13:40-42, it seems that it will be done by the angels. The expression means, as the withered and useless branches of trees are gathered for fuel, so shall it be with all hypocrites and false professors of religion.
[Are burned] See Matthew 13:42.
(from Barnes' Notes, Electronic Database. Copyright (c) 1997 by Biblesoft)
Both Jesus and Paul warn that there will be believers who fall away from the faith and by doing so become unproductive. OSAS totally ignores these warnings.