Strong encryption may be unbreakable in a mathematical sense but encrypted communications are not unbreakable in practice. Key extraction through side channels or compromise of communications by physical surveillance or evil maid attacks is practical. It just can't be done to a billion people at the same time. Read here https://github.com/maqp/tfc/wiki/Threat-model for an overview of all the ways an all-out, unusually secure encryption system (encryption and decryption done on separate computers with data diodes, 100% reproducible build) can be broken.