The problem with Bitcoin being a major currency is that the early miners have accumulated large portions of the total share of Bitcoin wealth. That's a fundamental problem that does not exist with fiat currency like money, and while many consider it an asset that Bitcoin's inflation is highly regulated, very few individuals would be comfortable with the idea that certain individuals would own billions or trillions of USD worth of them in the future. And that is what will happen if Bitcoin maintains its upward trajectory in value and more and more people use Bitcoins as a form of wealth.
What banks would feel vastly more comfortable with would be certain technological abuses of the Bitcoin protocol to make it a substitute for real money. For example, using the transactions to create cryptographic, trusted proofs of USD transfers with negligible amounts of BTC actually involved.
Yes, Bitcoins are the New Pogs, and some folks early on bought out the first few production runs of them hoping that people would eventually replace currency with their New Pogs. That notion should be deeply disconcerting to anyone who invests in BTC (either in mining or with money) because at some point those people that have a large portion of the total amount of BTC that can ever exist might decide to cash out or abuse the market.