It's not always easy to avoid banks. I don't like them much, for one, but use them quite often anyway. Because I receive my salary to the bank account, I need fiat to pay in the supermarket, for rent and transport. And honestly, even though I appreciate Bitcoin and don't trust banks much, I keep the money I cannot afford to lose in fiat, usually on my bank account. Because accumulating cash means that you'll have problems spending it on something big if you feel like it, plus flat robberies are way more common in my country than bank robberies. Moreover, in fiat at least I approximately know how much purchasing power I'll have in a year, whereas holding everything in Bitcoin is just too risky.