Monetary value and its instruments are amoral. They're neither good nor bad, so "weighing" their uses would be entirely unfair. The demonetization in India was a perfect example of moralizing currency instruments. (The IMF loved it because of the resale of data from digitizing transactions and India loved it for tracking people's financial habits. Modi loved it because it punished poor people.)

If you're trying to ban cash because you can buy illegal things with it, then you have a logic problem.