There is absolutely no reason to snail mail a copy of an FFL.
They can fax it or even email it to the seller.
Yes there is!
In one case the FFL holder wouldn't fax it himself,,,
But also some sellers want the copy to be signed by the dealer,,,
And they often will not accept a fax or e-mailed file,,,
They want an orignal signature.
You can cry BS all you want,,,
But the seller holds the cards and calls the shots.
When I purchased my first gun from Budsgunshop.com,,,
I didn't know about the Evil Pawn Shop in my town,,,
Buds asked me to snail-mail the signed copy.
Now they have the Evil Pawn Shop on file as a cooperating FFL holder,,,
I've ordered 7 firearms from Buds and all have taken under 7 days,,,
Except for that first one when I had to snail-mail the FFL copy.