The banks, on the other hand, are very easy to "kill" — just stop using them. Unlike the government, they have no way to compel you.
Yes, "just" stop using them. Like we can "just" stop voting in all these rubbish politicians.
Most people can't stop doing business with them because they are already in debt and clearing that debt will take decades. Even if not in debt, not having a bank account and debit/credit card(s) and other financial services can cause you all manner of difficulties.
Banks, on top of providing essentially services, have built a money sucking machine. And they've made very sure to entangle the leeching part thoroughly in with the good bits.
The only way to address this, without plunging the economy into chaos, is for the government to step in and untangle it (cutting the proverbial Gordian knot). "Just" not doing business with the banks will either accomplish nothing (because you can't get enough people involved) or will precipitate a financial collapse.
Unfortunately, getting the government to do something about this "just" requires us to vote some decent people into office *sigh* yes, "just".