If you don't receive your salary paid in bitcoins and if you can't use your salary everywhere you will still need to use a bank.

Otherwise how do you plan to receive your monthly cheque or how do you plan to pay the recurring payments to pay the bills (water, electricity, ISP, phone, insurances, taxes, landlord...)? If you can not pay the groceries how will you pay the cashiers?

How businesses could be created if they can't borrow money from the banks? It's what makes an economy growing, create jobs, etc
What about the average Joe using his interest account to earn a small profit annually? He won't have any opportunity. The amount collected with the interest accounts from banks is also used on the local economy, to build houses for the average class for example.
The average Joe won't be able to borrow money to buy a car to find a job, or to build his own house.

Bitcoin isn't looking to replace the banks but rather to be an alternative, as a second layer (or as the first, as you wish)