The CIA (and etc) need secure, reliable, public communications to exist, in some measure. If their agents are the only people sending encrypted traffic, that's

The CIA (and etc) need secure, reliable, public communications to exist, in some measure. If their agents are the only people sending encrypted traffic, that's bad. Gotta have some cover. If you can harvest the other users' conversations, thats a bonus but one thats hard to use. because of the risk of tipping those users off to the fact and having your cover traffic vanish.