For me i used both, i have bitcoin for my investment and sometimes i used this for paying my bills because there is a rebates in every transaction i made then i have bank account for my savings that i want to earn some interest with it and also for my future.
What's your method to paying your bills, maybe I never heard about the people can paying their bills using bitcoin indirectly the form of payments, I always sure they always need a bank account to paying their bills every month.