Not as simple as that as many did ditch WahtsApp for Meta’s documented privacy violations, and their ongoing T&C which passes the WhatsApp metadata upstream to Meta and others. A lot of people also only use one messenger, and right now nothing connects them together yet. So I have masses of family and friends that only use WhatsApp, and I now only have SMS contact with them. About 8% to 10% do have multiple messengers so I see some on Signal and Telegram.
The last thing the world needs, is for WhatsApp to become the default dominant standard. That is a company that can be least trusted out of everyone worldwide, based on their history. With the app installed, the metadata includes constant location, usage, contacts, messages to who, etc.
Yes I was too, that is the client end-point that everyone is after now, and where Meta was trying to spy on Snapchat, and where State Actors get into encrypted data before it gets encrypted. It’s the known weak point, as you read everything unencrypted. But it also comes down to who would want to read your data and why. Are they legally empowered/prevented from doing so, do they sell data to data brokers, etc.