This reminds me of old websites blocking right clicking on a webpage since that's how you viewed the source code, yet there's always a way to get the source. Same in this case, there's always a way to capture the "protected" content.

Edit: granted, not only old websites do this. Instagram lays a full width/height transparent div atop the picture to prevent right-click copying of the image.

Except the platforms are getting better at it. Android has an API which allows apps to completely block the screenshot functionality. For the average android user, there is no way to get around this. Computers are getting locked down more and more to the point where these kinds of restrictions actually start working.

Yeah, it's so tiresome. It's my device, I should be able to do anything if I want to. Then Android comes up with some API to let apps subvert my will. Who cares if the app doesn't want to be screenshotted? I'm the user. What the app wants doesn't matter, it's never mattered. I could fight this by rooting my phone and using custom implementations that lie to the apps and only pretend to be secure. Then Google comes up with hardware attestation and now there's no way to fake things anymore. It's like we're the enemy that the phone is being secured against. I barely have words to describe how much I hate these companies and the way they try to control me.

We have free software everywhere except phones. I wonder why organizations such as GNU aren't working on free software clients for these popular services like WhatsApp and Telegram. The potential for a positive impact is enormous.

https://github.com/telegramdesktop/tdesktop

https://github.com/DrKLO/Telegram

https://github.com/TelegramMessenger/Telegram-iOS

Plus a few web frontends, I am way too lazy to find them all.

https://github.com/zhukov/webogram

WhatsApp forbids third party clients IIRC.