https://wikipedia.org/wiki/Shaka_sign

That goes hand in hand with a level of trust with some companies/people and everyone has different threat tolerances. It also highlights the mindset that you have no idea what the person on the other end of the message is doing with it. End to end encryption helps keep in line eavesdropping down but if the recipient of the message has a compromised device or are screenshoting everything and posting it on facebook it’s out of your control.

As someone else said, selfhosting is the only real way to overcome this problem. When it’s all on your hardware it matters a lot less if the messaged at are decrypted server side or not. Everyone has a different threat level and at some point you have to put trust in some companies but if beeper makes you uncomfortable then buy a cheap second hand mini pc and learn to self host the service.

I’m no expert but my understanding is all drinking cans are lined with plastic to withstand erosion.

https://www.ehow.com/facts_7390219_metal-cans-lined-plastic-coating_.html