The person who pays for insurance is the one who gets reimbursed if there is a loss
You are 100% right, but the problem comes when a seller thinks its over when he drops it off at the post office. Some do not package well, or make it really obvious what is being shipped, etc. When the seller thinks its out of his hands at the post office, then he doesnt want to pay for insurance. The guy recieving it cant buy insurance or make a claim because he did not own, package or have the item shipped.
