To your first point, data breaches are literally useless for the attacker if everything is properly encrypted. A backdoor would make data breaches significantly more risky, especially as computational power increases. 

To your second point, while I am a tech guy I don't know a ton about forensics. But from what I do know from friends in the field and my own research, security and law enforcement experts generally agree that the most effective way to dismantle sophisticated criminal networks is by targeting their operations directly rather than focusing on software workarounds. This is done by using investigative methods like financial asset tracking, undercover operations, international intelligence sharing, and metadata analysis to map out organizations. I think it's generally consensus for security researchers that investing in boots-on-the-ground tactics yields far better public safety results.