To keep sellers honest, we have a policy of reporting reclaimed accounts to game publishers. We also have technology which keeps would be repeat offenders from ever doing business with us again. Scammers get the boot, permanently. And they're left empty handed because the account gets banned.
As a seller, you have 100% security. As a buyer, you may want to buy the insurance. We figured out the typical loss rate (about 5% industry-wide), so we how much to charge in order to cover the cost of any reimbursements which need to be made.
We thought about making insurance purchases mandatory, however we like to leave that up to the buyer. 100% your choice if you want to spend on protection.