Banks are designed to provide safe protection for people's money and to lend to those in need at a certain amount of interest or dividends. Bitcoin, on the other hand, is an investment system that is controlled by a decentralized authority and consensus. So, as Bitcoin has a different ecosystem than normal banks, the two cannot completely substitute for each other.
You are right, both bitcoin and banks cannot replace each other because they have different functions and ways to be a member in it and how to use it. Bitcoin simply created as hassle-free in digital processes such as payments, investment, sending money and other thing while banks needs documents in order to process everything where your money keep safely in there.