Why are all of the events listed as "All Sales are Final"?

We are a volunteer-run organization with no administrative help.  As such, we book all events and venues, as well as process all refunds ourselves.  At most venues, we are obligated to a minimum attendance guarantee, otherwise, we may lose our deposit.  When we allowed refunds in the past, we found many people cancelling at the last minute, and thus, we lost a lot of money.  In most cases, if you're unable to attend an event, you can have someone go in your place.  Simply change the name on your RSVP.