I guess it's because of Fatal's style. His rhymes are always pretty dope and multi-syllabic, and the greater amount of thought necessary to make stuff like that along with the fact that not all of his stuff has been officially released to the public (as someone mentioned before, stating that only hardcore fans will recognized recycled verses), he might as well re-use a verse or two here and there. Most people can freestyle all day long if they want to come up with simple rhymes that just rhyme at the very end of the line, but to come up with more complex stuff takes more focus.