I think some buyers are concerned about re-routing scams so they do not provide the tracking until its delivered to show proof of delivery.
I ended up losing a few BTC on Purse (buying BTC) since I have had a handful of users say they haven't received package, although tracking shows delivered, or no tracking (some 3rd party sellers don't post) but no return.. Purse tends to side with the receipients and Amazon is strict about that, make the claim more than a few times and they will hold/close your account.. I'm tired of the bullshit Purse threw at me over a number of transactions and the apparent assumption the buyer is telling the truth, over 200 TX without a single negative feedback but I am staying away for now.
I'll add to that, some of the gift cards I purchased on Purse a couple of months (purchased dozens) ago have been flagged as invalid, downside is Amazon rarely tells you which ones,'still fighting that problem now, lost a few more BTC that way.. Purse made a good move in disallowing purchases of them now, but it sure provides some insight into a set of users on the site..
This is a bad story about purse, i have read also in reddit i think about a similiar story when he had trouble with the item that he bought in amazon through purse. I would sell the bitcoin for paypal or cash and purchase items as usual.