1. How is this really different to government-mandated microphones and cameras in your house, school, workplace, etc? 2. What’s the endgame here? Open-source encrypted messaging software is widely available. The cat is out of the bag. Every country on Earth could outlaw the technology and it would still be trivially easy for criminals to use it. Do the people behind these proposals not see that?
You don't have to mandate something that people have done voluntarily. Mobile phones are cameras and microphones in every house, school and workplace. All the mobile standards have "legal intercept" provisions, which basically allow law enforcement to listen to your conversations / read your text-messages. This is just a demand to go back to the status quo ante, where Government had unrestricted access to all your phone conversations and mail if they chose to.
I would also wager that there is a non-zero chance that the baseband processor of all phones has a backdoor, which is why the US can't allow phones to predominantly use Chinese made baseband processors. The baseband has access to your microphone and camera and is mostly out of control of the application processor.