Trust is an appropriate metric to consider. Often, the matchmaker company isn't being evaluated on material criteria like performance; they're contracted because there is some preexisting relationship (not always direct) between decision makers at the two firms, or because they hold a certain reputation. You could say that risk to firms are lowered because liability is transferred, but that's sort of orthogonal to my point that the point of existing from the point of view of the middlemen is not to trade in risk but it trust. Risk is a commodity, trust is scarce.
