The key is in the penultimate question. If GCHQ/NSA is interested in surveilling a specific individual, you'd need a lot more than this software to communicate

The key is in the penultimate question. If GCHQ/NSA is interested in surveilling a specific individual, you'd need a lot more than this software to communicate securely, because there are just so many vectors. This solves dragnet surveillance, where the government could potentially just sniff all communication and use various analytical techniques to sniff out potential criminals or people they dislike.