Why Purgatory?

32nd Sunday in Ordinary Time This last week we celebrated both All Saints Day and All Souls Day.  On All Saints we rejoice and thank God for those whose souls are fully united to God in heaven; on All Souls day we pray for those people who have died and whose bodies are decomposing yet whose souls live on into eternity.  Why do we pray for them? What need would they have that we can help with?  Why not just celebrate All Saints Day and forget about All Souls Day?  When the word "purgatory" gets brought up in conversation I'm usually met with incredulity, people thinking of it as an outdated or unnecessary idea - if God is love why would there be a purgatory?  But maybe the way we're thinking about it is all wrong; maybe there's something incredibly relevant and timely about purgatory, both for us and for all souls, whether living in the body or out of it.