Another aspect of bitcoin, is that it may mature into the low-level payment system for the planet, with a higher-level payment system (which has chargebacks etc) layered on top by financial institutions.  How does this work ?

Well TCP/IP , the protocol that runs the Internet delivers packets with a guarantee of delivery.  It's implemented by TCP layered on top of IP which delivers packets with no such guarantee.  It's technically hard to jump to the second layer in one go, much easier, more robust and flexible to build IP first, then add the TCP to produce a reliable system.

The real world of banking has a payment system.  In the UK it's mediated by the clearing banks.  It is not transactional, and has some pretty serious flaws in it (which the banks largely deny).  Bitcoin could be a feasible replacement for such a service.

This is not to say that bitcoin cannot do the higher-level work to, but at the bedrock of finance, a non-reversible, transactional system is essential.