This is only partly true for telegram and the fact that people repeatedly get it wrong is more harmful than if Telegram wasn't encrypted at all and everybody would know it.

Telegram use end-to-end encryption only on so called "Secret Chats".[0] And in my experience very few people use "Secret Chats". This is the main reason I don't use it anymore and recommend against using it to others.

[0]https://telegram.org/faq#q-so-how-do-you-encrypt-data

WhatsApp is also encrypted, but it does share your data with Facebook. So while end-to-end encryption always sounds secure, it not always is.