Encryption shifts the economics of attack.
Plaintext can be slurped up by dragnet surveillance and analyzed at the attacker's convenience.
Transport-layer encryption makes passive attacks ineffective, forcing governments to attack the servers to spy on everyone.
End-to-end encryption like Signal forces governments to choose their targets and expend resources on attacking each one, proactively.
The more people that use E2EE for traffic the governments aren't interested in, the more goddamn haystack there is to sift through in search of needles.
The economies of scale go away if the E2EE makes popping servers useless to the governments. This is why I insist the centralization of Signal is a red herring.