How is cash faster and more efficient for eCommerce than Bitcoin?
I'll explain - use payment system, epayments - all transfers are instant, no fees and is not limited in amount. That is, if two recipients have e-payments accounts, it's all done very quickly and for free.
Cash is not the same as an electronic payment system.
Efficiency is a relative term. And those systems are by far not free.
You might not always have to pay a fee in $ to transfer money. But you pay with your privacy.
Those services (hello paypal) track every activity. From IP you login from to amount of time it takes you to click a button on their website.
A centralized system has a huge amount of contras. Each system has its pros and cons.
For people who care about their privacy and don't want 3rd parties to have more information about them than anyone else,
such a centralized payment system is a no-go.