sgc...what am i missing

[sflayank]

they've been in business for 20 years? give or take
yet the new holder has only been out for 6 months
or 3 % of their lifespan
but ive noticed that in recent auction catalogs a very high % of sgc cards are in new holders
for instance huggins last auction that just ended there were 83 sgc baseball cards in the catalog....77 of them had new holders...more than 90%
same is true for other recent auctions
so where did these "new" cards come from?
lets look at the possibilities
collectors decided to reholder their cards and sell them immediately? unlikely
collectors liked the new holder so much that they finally sent in their cards and decided to sell them? also unlikely
dealers sent in some old stock thats been lying around gathering dust? i guess thats possible....unlikely for expensive cards however
so where did these new grades come from? and who is selling them?
any thoughts?