Chats are encrypted. The question who can decrypt them by default.
It is a trade-off between security and usability. By default, you get usability (e.g., you can chat across devices easily). But you think it is worth the cost, you can make encryption keys unavailable without corresponding devices (create secret chat).
My guess, most telegram users prefer usability or don't care/ignorant. It would be a mistake to make the experience worse (that people would notice ignorant or not).
It is false that chats are "unencrypted" (I know, it is repeated on every submission about Telegram here but it does not make it true whatever Goebbels said). Here's a quote from the FAQ: "The relevant decryption keys are split into parts and are never kept in the same place as the data they protect. As a result, several court orders from different jurisdictions are required to force us to give up any data." https://telegram.org/faq#q-do-you-process-data-requests
That is only true for the End 2 End encrypted chats, which are a separate and not very user friendly thing. Regular chats and group chats/channels are by design unencrypted.
Then it is not correct. A security analysis of Telegram has raised doubts about their e2e before. They have (had?) a blogpost up where they pontificate about how it not necessary and would put a burden on their channel feature anyway.
It is a trade-off between security and usability. By default, you get usability (e.g., you can chat across devices easily). But you think it is worth the cost, you can make encryption keys unavailable without corresponding devices (create secret chat).
My guess, most telegram users prefer usability or don't care/ignorant. It would be a mistake to make the experience worse (that people would notice ignorant or not).