Ok, fair enough.
They’re a messaging platform. They need to store the messages in order to allow you to read them. Note that the retention period on messages appears to be fairly short. Probably a month or two weeks. I don’t understand what you find objectionable here.
Would it be possible for them to not store the messages for a couple of weeks? Sure, they could require both users to be on-line when the message is sent and have them be totally transient. Or they could do end-to-end encryption, but that ends up being either security theater or totally unusable for a normal user (has anyone reading this ever actually verified the e2e encryption status of a WhatsApp chat?). Both of these would make for a garbage user experience in a multi-device environment.
I think this is where our fundamental disagreement is. You appear to be opposed to absolutely all kinds of user data being stored. Doesn’t matter how beneficial it’s to the user, or how fundamental it’s to the service that the user is actually wanting to use. That seems counter-productive. “Our vision is for Gmail to delete all your emails before you read them, for Netflix to never remember where you left off watching Star Trek Discovery, and for Amazon to always challenge you with extra verifications when logging in since they can no longer do sign-in risk analysis.”. That sounds like a horrible deal!
There’s a sharp contrast to things like Facebook promising they were collecting phone numbers only for second factor authentication purposes, but then covertly using those numbers for building their social graph. Or silently hoovering up your SMS message history from the phone if you install the Facebook Android app, and keeping that history forever. It’s not somebody collecting data necessary for providing a service, and keeping that data around as long as is reasonably needed. It’s fooling people into giving away data they didn’t expect, and then using it for absolutely any purpose that the company feels like.
Equating these two categories just means that people will become fatigued and stop caring about the second one.