Why do you avoid Telegram, arguably one of the best cloud messengers?

I avoid everything else apart from Signal (this includes Telegram) because with Signal I trust that they have:

- end-to-end encryption enabled by default, and as far as I know there is no possible way to disable this even if I wanted to.

- no logs/state stored server side, or at least that's what they claimed.

- no SPAM. The only people that talk to me on signal are the ones I actually intend to talk to. Not sure if this is just because so few people use Signal or because they don't have a chat-bot API they try to push as a commercial offer.

- a non-profit organization structure, not that being a for-profit is bad, but I tend to trust non-profits more when it comes to things like respecting privacy as a core value of their business (a for-profit would scrap that and abuse their market share at the snap of a shareholder finger).

No end-to-end encryption per default, and if I activate it I’m not able to see the conversation on other devices. Signal does that better.

I don't know anyone who uses Telegram. Everyone I talk to uses SMS/iMessage, or maybe Discord (but that's a pain in the butt for individuals).

I use Whatsapp, Messenger and iMessage. Simply because they are convenient and there I can reach ~95% of my friends.

their encryption is closed source. If we don't know exactly how Telegram works at it's core, any encryption it might have is almost worthless IMHO. Signal and Keybase FTW

I don't. Why do you think people avoid it?