Am I ..
Verbal agreement
People enter for many reasons
People enter into an agreement for many reasons
Yet leave for better or worse
I hold the stories, greedy seasons
If someone breaks it, its usually that he is better off without it, and maybe because of his personal greed.
Sadly, I know not a verse
But I would if I'd lived as a tree
A verbal agreement is not written anywhere, thus no one can prove it even existed
OR
Am I ..
A Shredder
--EDIT--
A toilet seat, people enter for many reasons(duh!), greedy season(for sure, everyone enters for their personal greed). It' helpful, used often everyday, greed is important(why would anyone sit on it otherwise). OR Maybe its the "Iron Throne", who knows.