Not supporting E2EE (cite: Telegram is not E2EE) and E2EE being not on by default are two very different things.
Not being on by default has an impact on other things, that the users value more. If they were on by default, they would lose it and Telegram would lose part of its appeal. This way, users themselves can choose the trade-off they are happy with.
It's bothersome that you don't admit that your false statement was false and continue to double down with irrelevant discussion. Telegram has E2EE therefore you are wrong.
"Telegram is not E2EE" is factually incorrect.
WhatsApp has E2EE however it ships your private keys to cloud storage by default. So it's even less secure than Telegram.