In my case...

Dunno. Force of habit? Congenital idiocy? 
Terminal laziness? 

Short term memory loss? ("geez, I should sign up 
with Anime Chaos" just as a cel i really want is 
about to end... only to be forgotten immediately 
after the bid is in.)

Yep, I'm paying more than I need to.  They've 
never given me any problems, though.