Are their any Obsessions that people have the you just don't get?
some of the Furs Doing it to Put a Smile on kids Faces that Have had a Bad life and it's like Anime Costumes in a Way most of the Maker Make Costumes for that they have had a Bad life and want to end it all but injoy making costumes to take the edge off the bad day that had so they don't get into drugs or it keeps them from ending there life.
I know from that I'm a Costume designer and I Make Anime Costumes and Fursuits for people it just a way to get throw life I had a Fursuit and the One thing that made me feel good was to see the Kids hug me and smile my friend when to different place like children Hospitals and children operational to put some smiles on the children faces.
if you still don't get it try doing to a con or two then you'll see that it just fun and makes your life just that much more fun.
and here is a Documentary on furries on youtube called
Furries - An Inside Look By Curt Pehrson
that well help you understand the fandom more then anything