Let me preface this by saying I work in security and use Signal. That said, the security industry can be incredibly obtuse at times. End users don't care. Full stop. Having the best encryption isn't a selling point to the masses. I'm making a chat app right now and I'm doing it exactly the same way as Telegram, unencrypted by default with an E2E private chat option. Why? Search. I don't need E2E. I use it based on principle. I do need to be able to search my conversations. As long as the chat provider is trusted, I'm happy to have my messages in plain text to be searchable and I think 99% of end users feel the same way.