Considering some of the largest app markets are not run by US (or EU) based companies (e.g. China), the assumption of control is also a fallacy.
"If you make encryption-by-default impossible, the amount of unencrypted messages will increase, and you'll have gained those."
Requires you to monitor every message for every form of data, and assuming the false assumption that banning encryption increases the simplicity of finding messages, you would probably only find more things not related to what you are looking for. Only assuming you have control over all data channels, which even the US doesn't have.
On the other hand: This message is then flagged: bomb, truck, explode. While you could better be looking at other stuff like origins and communication contacts. These give a clearer view than the random words you will be picking up, even when they are encrypted.
"If you make encryption-by-default impossible, the amount of unencrypted messages will increase, and you'll have gained those." Requires you to monitor every message for every form of data, and assuming the false assumption that banning encryption increases the simplicity of finding messages, you would probably only find more things not related to what you are looking for. Only assuming you have control over all data channels, which even the US doesn't have.
On the other hand: This message is then flagged: bomb, truck, explode. While you could better be looking at other stuff like origins and communication contacts. These give a clearer view than the random words you will be picking up, even when they are encrypted.