You literally cannot prove it either way, you can't prove it's not enciphered data, you can't prove it's not random garbage, that's the point. You can say that 'we could develop a safe backdoored system that will allow only lawful decryption in the event of emergency' in the same way you can say 'we can launch probes made of candy to distant planets that will build cities and plant potatoes for us'. It's a fantasy. The keys will leak, criminals etc will still blend into the crowd.
They are certainly enforcing the laws against selling and purchasing drugs. It is uncharitable but if the state actually cared about people it would treat drug addiction as a health issue. It can be treated, current policy obviously has done nothing to solve the problem in the US. The police are enforcing the supremacy of the state, these people are flaunting the law and must be punished otherwise the government looks weak. Nobody wants to admit defeat because it is admitting they are much less powerful than they want people to believe they are.
All of this is conjecture and would of course be unconscious motivation. People want to think they're the good guy, people justify what they're doing so they can sleep at night.