Thinking that Bitcoin can annihilate banks out of existence is waaaay to over enthusiastic. I'm totally sure that Bitcoin and cryptocurrency will disrupt and alter the financial markets far more in the future than at present, but to assume that Bitcoin can wipe banks off the planet totally ignores that banks are the cornerstone of a global economic architecture backed by the world's strongest and largest military forces.
Bitcoin is a huge competitor with normal banks because once people know that with btc they can fully control their money and spend it whenever they want unlike banks which one does not have any control over his deposited money and banks may create restrictions and limits that prevent him from using his own money, once more people feel the difference, they will abandon banks.
You must pay your taxes in fiat - this is principal means through which the monetary system grew, spread, and became entrenched. I dont see BTC becoming the universal medium of taxation anytime soon. This is in no way a criticism against Bitcoin, but a caution against losing track of sensible realism. The state maintains a monopoly on legitimate violence [Weber], it can and will enforce its desired monetary form. Bitcoin is an excellent alternative which exists concurrently to such, but will not replace such.