because if you have nothing to hide, you have nothing to fear, citizen! Why do you not trust the seasoned and and professional opinions of your government? Are you planning seditious activities, citizen?
/s
if you want the real reason(s), it (they) are because incompetent people cannot accurately evaluate competence, in addition to their having paranoid fears about average citizens not being in absolute terror of their government. Citizens that can freely communicate without being spied on are able to discuss any topic, including any topic the government finds disfavorable. That frightens power hungry morons like the people running our government.
The actual reasons why we truly, honestly, and without question NEED good encryption, is because the average cyber criminal is sophisticated enough to steal thousands, if not millions of passwords, credit account credential sets, and whole user identities, and do so *trivially*, without it. The average user is naturally a little untrusting of government, but is MUCH LESS trusting of the "Nigerian Prince", and for demonstrable reasons. (Yes, people still fall for that old yarn, I know. PT Barnum put it succinctly I think.)
The idiots in government apparently dont grok how encryption works, and think it is analogous to physical security, when in reality it is just really complicated math problems. As a consequence, they talk of absurdities like "back doors" and other moronic things, when suggesting purposefully useless encryption that is trivial to break. Naturally, they have yet to address the reality that if it is trivial for them to break, it is trivial for criminals to break too-- but that detracts from the narrative that "good guys need a way in to stop the bad guys!" Maybe if they were better at reducing the activity of those bad guys we already have, and NO, not fucking ISIS, I mean the damned Nigerian Prince, and those idiots that steal credit card numbers, people would be more willing use weaker encryption-- but no, they are simply too incompetent for that.