ZCash's biggest problem from a common man's perspective: It's privacy isn't enabled by default, it's opt-in. That means, people (i.e. the people you are interacting with) need to opt-in with it's privacy, in order for you to be able to achieve privacy.

I have the same problem with Signal, it tries to be 'seamless' in it's integration with SMS. But now I could be talking to someone on Signal who also uses Signal so the communication is secured, but if they don't, Signal just sends messages as an unsecured SMS (though it shows you on the app with a slight UX tweak that this is an unsecured communication channel, but that's not good enough).