I'm against this for many reasons related to increased potential for authoritarianism and abuse of freedom, but also because it undermines a desirable quality of cash: if our digital infrastructure suffers a significant outage, physical transactions must continue. We must always be able to "bootstrap" back from the physical realm while we repair the digital realm. If everything moves to "ecash", that becomes impossible. It makes us less robust. It's like putting the recovery codes for your password manager inside your password manager.