For a small (very small IMO) percentage of buyers I guess that is true, but the buyers in my situations are not using the system to get a refund, they are not even responding to accept the offered refund, they are not trying to gain anything for nothing, so I'd hardly call them scammers.  It's more like they just assume the seller is a bad apple and couldn't be bothered seeking a resolution, just neg them and move on.  BTW, neither of mine have a long history of such action.