An analogy I use to explain to people who don't have a technical background is, "Imagine if we made it law that every pen ever made was required to be chained to a special clipboard that makes a carbon copy of whatever the pen writes." Even when explained like that, it's clear how such a system could be bypassed and would only harm innocent users, but even worse is just how ridiculous it all seems, since this would all be because we can't subpoena a pen. Hopefully it's made clear that despite the subpoena being lawful, it simply doesn't make sense, and attaching this fictitious clipboard doesn't really help make it make more sense, since it seems even more ridiculous once it's made clear that you can't subpoena a pen. It's no difference than saying you can't subpoena math, and that's OK.
I hope as we progress technologically, every day users will understand encryption to the point where they can form their own analogies as to what a ban on encryption would even imply.