> Why isn't this middle ground being discussed?
that's what they need to do even today after they have found enough evidence that the court sent you what's called "notice of inquiry" and preliminary investigations start (it doesn't mean yo are guilty, it means there's gonna be an official investigation on you and after the investigation has ended they're gonna either drop the charges or go to trial).
but crime prevention usually works best when investigations are kept secret.
Imagine if in Italy we called every mob boss the police was investigating on to tell them they were tapping their phones or checking their bank accounts.
They knew it anyway, but that's where the middle ground is.
Another possibility would be, as I've written somewhere else, that a pair of keys is always created and made available to the local authorities, but they have to be authorized from a judge to use them.
The encrypted data is instead kept on the provider side, so that even if someone steals the keys, they can't access the data because it is in a separate facility, protected in the same way it is today, because it's in the best interest of the provider, that is already collecting that data, to keep it safe.
And if someone steals the data, can't decrypt it.
Metadata are also very important to investigators, I imagine that their need to decrypt the conversations comes from the fact that with the metadata they can narrow down the number of suspects to a few, but without the actual content they can't tell exactly what's going on.
> if they read the messages and find you've done some crime, authorities will eventually track you down
that's not so obvious.
I could show you a lot of cases when this has not happened, for various reasons, most of them formal (tapping lasted a few hours more than authorized, tapping was badly misreported in some other meaningless section of the conversation but it's enough to nullify it in its entirety, tapping included someone else that was not under investigation that should have been removed from the records bu it's still there, etc. etc.)