The only way you could live off cryptocurrency would be if you had millions of dollars invested into it. With crypto's extreme volatility, the average individual finds it hard to achieve a stable income to survive in the mainstream world. Those who want the convenience of Fiat and crypto, would definitely rely on both Banks and cryptocurrencies. Without a bank, one couldn't interact with many businesses and merchants available worldwide. Banks are the gateway to Fiat currency, so they're still necessary even if crypto provides greater benefits.
Cryptocurrencies like Bitcoin and Ethereum, may be the most popular ones in the world, but they're still not widely adopted by mainstream businesses. There needs to be stability, reliability, and scalability for crypto to achieve said purpose. Many exciting things are yet to come such as the Lightning Network, Sharding, Plasma Framework, and more. With these improvements, and proper regulatory compliance, crypto could become the top choice of merchants and businesses worldwide.
Despite this, one cannot deny the fact that Fiat will always exist for years to come. Hence, Banks will never replace crypto and vice versa. Just my thoughts