^^^^This^^^^ hits the nail on the head, and the comment made about reputation.
As a seller, I like to have my item packed and ready to for a label before I list it. You never know how fast it's going to sell, and I've had to scramble looking for a box when an item sold right away and it wasn't packed. The buyer has to wait and you look bad. Sometimes life happens and you can't get the item out right away, and that's when you reach out to the buyer to let them know. I've never had anyone get upset when there was a delay, and they always appreciate the heads up.
As a buyer, there's always a risk but being familiar with members around here really helps with peace of mind.
I personally wouldn't have publicly blasted the member so soon after the deal, but everybody's different.