For what Telegram 2.0?

Many people are understandably puzzled and ask: why enter the crowded messenger space?

Telegram is an excellent messenger with a huge feature set: bots, TMAs, a built‑in Web3 browser, Instant View. There are so many features that listing them all in one post would be difficult. It's a great platform, so why build a separate TON Messenger?

It comes down to privacy.

Telegram (MTProto 2.0 Part I Cloud Chats) uses client‑server encryption. This is not end‑to‑end (E2E), it's point‑to‑point (P2P) encryption. This means that your messages from private one‑to‑one chats, groups, and channels are in plaintext on Telegram's servers after receipt.
Messages are additionally encrypted on the server so that a database compromise without Telegram's keys would not let an attacker decrypt them. But this does not change the fact that Telegram already has the full context of your message.

E2E encryption is implemented in MTProto (Part II - Secret Chats), and according to the official source they are gaining popularity.
However, we looked for usage statistics for Secret Chats and found none.

Secret Chats have several drawbacks:
— No support in the desktop app on Windows and Linux, which together account for ~70-80% of desktop operating‑system market share
— No multi‑device sync
— No reactions and some other conveniences available in Cloud Chats
— Private group chats and channels still lack E2EE

Note: End‑to‑End encryption is on by default for one‑to‑one voice and video calls, which is great. It is absent for group calls.

To sum up: you can switch to end‑to‑end encryption, but you will lose many messenger advantages.

This is not an expose of Telegram, because everything cited from official Telegram public sources.
But many regular users are under the illusion that private one‑to‑one chats and Secret Chats are the same. We simply want to remind you that the classic mode of communication most people use in Telegram is not private and not fully secure.

Pavel Durov has already answered the question "why isn't end‑to‑end encryption on by default":

So after some research we decided to introduce 2 kinds of chats – Secret chats and Cloud chats.
Secret chats are e2e-encrypted chats that never under any circumstances get backed up.
Cloud chats are encrypted in the same way, but also have a built-in cloud backup.

The phrase "encrypted in the same way" is the core sleight of hand/wording error here.
End‑to‑End encryption in the context of messengers means a message is delivered from one client to another without decryption on the server. In Telegram’s case, this rule is broken for Cloud Chats.