If your contacts do not use Telegram, then you're basically ****t.
For example, in South Africa I have never heard anyone mention Telegram at all. I bet there are very few users. On the other hand, "everyone" with a Whatsapp-capable phone is on Whatsapp.

I am not advocating for Whatsapp, which I've never really liked to use, but, as a person you want a "network" where people who matter to you also use.

Not saying Telegram is not useful