I don't think they -intentionally- exist to harvest user data. They just create a situation where they can be taken over by an entity that wishes to easily at any point, or maybe they are already tapped by an entity that has dumped their SGX keys and/or is tapping their network traffic to bulk harvest the metadata they helpfully centralize.
The founder of VK had good intentions and was willing to protect his users too. The Russian government replaced him with someone more ethically flexible.
The foundsrs of WhatsApp clearly never intended it to go in the direction it did post acquisition, but it was not their call.
Gathering all users to a single choke point on a single client on a single server infra is irresponsible and unsustainable. We have been here before.
