Which many members of conspiracies would be more than willing to do, hindering the investigation of organized crime, and (genuine) terrorist cells.
If your argument is that they're willing to face the consequences in order to perpetrate their greater crime, then (respectfully) you've missed two crucial points:
1. US legal tradition wholeheartedly rejects the goal of absolute security. Better to suffer a few terrorist attacks than live in a surveillance state (yes, yes ... I know... not the point...)
2. Deterrence, in general, doesn't work against self-sacrificing adversaries. Even if crypto were outlawed, terrorists would still use end-to-end crypto, and refuse to comply with a court order to decrypt.
The great issue here is the total unbreakability of crypto when compared to e.g. a safe. Before this, all we had was human memory which is very limited.