gee could it be something to do with bitcoin being very difficult to prove ownership or transference to a third party? I think it is.
Yes, it's difficult, but blockexplorer.com is a life-saver. We have even won PayPal disputes for our Mining Rental Contracts, where there is no physical item shipped, in part because blockexplorer.com was able to identify the transfers.
The future of crypto currency safety on chargebacks lies in a tool such as the blockexplorer. If when, where, and how much are decided in advance and made public or at least held by a trusted third party, then chargebacks can be fought because you can prove that you held up your end of the agreement.