How will you enforce 'limiting encryption'? Will you prosecute everyone who runs a few mathematical calculations on their own computers, presuming guilt?
Do you think that criminals will care that it is 'illegal' to send messages when they're plotting more heinous acts? In such a scenario you'll have to radically enforce what programs may or may not be run on everyone's computer. If you do that, you're worse than the criminals.
> Do you think that criminals will care that it is 'illegal'
If that sort of logic were to be applied what's the point in any law? Deterrence, making it harder, and punishment. Rolling your own crypto is hard, just like building your own gun for a robbery is. Not impossible, but it will certainly deter less motivated individuals. If all crypto was broken with law enforcement owned escrow keys (not in any way advocating for this, just playing devil's advocate, criminals would know not to rely on it and would have to first build a reliable safe method of communication (like physical meetings). Not the end of the world, just a deterrent.
> In such a scenario you'll have to radically enforce what programs may or may not be run on everyone's computer. If you do that, you're worse than the criminals.
That's a wild exaggeration. All sorts of things radically enforce what software can run on anyone's computer (DRM, antiviruses, licenses, etc.) and that's not great, but comparing that to an actual violent crime for instance is just stupid and honestly insulting.
Do you think that criminals will care that it is 'illegal' to send messages when they're plotting more heinous acts? In such a scenario you'll have to radically enforce what programs may or may not be run on everyone's computer. If you do that, you're worse than the criminals.