I use cash as much as possible because I have had my debit card numbers stolen many times. Sucks to get caught with out money when you are out of town because so jerk in Bahrain is spending your money.
If asked why you are using cash that is your reason right there. I need to ensure that I have money for gas to get to work so I keep a reserve at home is what you tell the government. In my case it is a truthful statement.
Not to mention that if there is a run on banks like they had in Europe you can eat and drive.