Until making a btc transaction becomes as fast and easy as swiping a debit/credit card at a point of sale, there is absolutely no motivation for customers to switch currencies. The infrastructure is already there; why reinvent the wheel? I agree btc is the more efficient choice, but unfortunately, it has a lot of usability issues to sort before it's ready for the prime time.
That's it, it's almost like a vicious cycle. Customers won't take up bitcoins until the infrastructure is there in shops etcetera and it becomes convenient, but businesses won't start accepting them until more people are willing to spend them.