For my business, I order thousands of items on Amazon and Ebay per week. Even with the protections in place, sellers don't ship the items and then never respond/won't refund, I get the wrong items/broken items (and they refuse to let me send it back). Why would I shop anywhere without these assurances?
In a normal transaction, once the item ships and is received, both the buyer and seller agree to the transaction and funds are released. If there is a problem, then that third party enters the picture, and sends funds from the multisig by agreeing with either buyer or seller.