People use Telegram because they have a great user experience. Signal, unfortunately, does not - and it's not entirely because they're limited by E2EE.
* I decline Signal’s prompt to turn on notifications with the “Not now” button (there is no “No thanks” button). It responds with “We’ll remind you later” and nags me again in a few days.
* I decline Signal’s prompt to share my contacts with it using the “Not now” button (there is no “No thanks” button). It responds with “We’ll remind you later” and nags me again in a few days.
Signal may be good at security, but whoever designed the app has no respect for users’ time, and it doesn’t seem like they respect a user’s privacy choices either. Telegram, on the other hand, does not have E2EE chats by default, but the privacy features are far ahead.