I suppose of Bitcoin anonymity you could say you can keep track of the contractor you paid the BTC to, but you can't tell where his employees buy their groceries.
Unless you bother to examine the public record of all Bitcoin transactions.
This implies that you need another agent to complete a Bitcoin transaction which is not the case.
Except that you need to broadcast the transaction to the Bitcoin network, which must then confirm that the transaction is valid. What I said is that most people rely on another agent to complete their transactions for them -- because most people want fiat currency, not Bitcoin currency, and they usually do not want to wait for confirmations (nor do they want to accept payments without confirmations) or deal with an ever-fluctuating exchange rate.
Most fascinating about Bitcoin is that you can have it in a sense that applied to gold more than say bank notes
Let's put it this way: try to use gold to buy a car, or even to buy something as simple as a single meal.