The perceived usefulness of a network, platform, or communication protocol increases with its relative adoption. That's known as "network effect", and network effect is at strongest for anything regarding direct communication - such as messaging platforms.
In other words: WhatsApp is used by lots of people, and this discourages people to migrate over better alternatives, like Signal (my choice) or Telegram (OP's).
The perceived usefulness of a network, platform, or communication protocol increases with its relative adoption. That's known as "network effect", and network effect is at strongest for anything regarding direct communication - such as messaging platforms.
In other words: WhatsApp is used by lots of people, and this discourages people to migrate over better alternatives, like Signal (my choice) or Telegram (OP's).