Merchants don't use google or amazon(or any other payment system) because they require a higher amount of reserve and/or fees. The loud complaints are from people who want their cake and eat it for free. People don't realize nothing is free.
Actually thats not true about dumping the whole problem on customer. A customer could be a buyer or seller, i believe you are talking about the seller. If you read the SEC filings paypal/ebay takes some loss based on what type of scam/stolen/other it is.