You appear to be speaking from a purely consumer perspective. That's being only the client in a client/server relationship, and feeling a need for protection from the supplier.

I'm speaking from being a peer; both a consumer and a supplier at the same time. We are more than consumers, we're people and citizens that provide services and utilize services of others. Having a third party in those transactions that can arbitrarily disrupt them has proven problematic (for reference, see all of the backlash against PayPal for the way they arbitrarily freeze funds on both sides, etc).