They said “no” because that’s the easiest thing for the pavement apes who work for the postal service to do.
The seller is out the laptop and the shipping cost. Not the laptop and $1300. It is possible(probable?) the recipient managed to get the laptop without signing. Or a post office employee stole it.
With the post office you take your chances. The mail gets there at least 99% of the time maybe more. It is useless to buy insurance through the post office and tracking is a waste of time and money also. If something gets lost you play hell finding out what happened, much less collecting on it.
That said, the cost of postage is a bargain.