you think governments aren't interested in analyzing the private communication of the population? There's a long list of intelligence programs listed on Wikipedia that suggest otherwise. Governments are obviously interested in both with interests going way beyond crime.
And another fact is that these bans can even give you access to the people outside of the law. Practical example, Australia's sting operation of pushing their own 'secure' app on the blackmarket to lure criminals in. (https://www.washingtonpost.com/world/2021/06/08/fbi-app-arre...)
You are not interested in just "people". You are interested in very specific subgroup of those (1-x)% that already operate outside the law.