That's one way to ensure you can make changes to your policies. If users can't access some features, they are likely to agree. Or they might leave the platform, but switching a communication platform is hard if the people you communicate with won't move with you.
I use WhatsApp often when I'm overseas, as people in other countries seem to like it. One of my kids also likes it, so I can send him message or make calls when traveling. I have other methods, but there are certainly some people who I only communicate with on Whatsapp, so I'll likely be agreeing to the new policy.
I do, however, understand people who are concerned about Facebook and privacy and more. I certainly am careful about what "data" I put on Facebook, and I expect anything I do could potentially be lost, so I'm not as honest as I might otherwise be.
This is potentially, however, a disturbing new technique for getting customers to agree with changes to a EULA that you might want to make. While many US companies just change them whenever they want, some regulations require opt-in of certain items. If a company thinks customers might not want to agree, and they start turning off features, this can put pressure on customers, especially those that might not have easily migrate. This is one thing for Whatsapp, but this could potentially be a more disturbing issue for COTS software your business uses. Switching platforms is difficult and expensive.
If we had more open standards for most data and software, this might be less of an issue. This would allow more competition among vendors, and force them to pay attention to security, quality, and privacy. If they didn't, changing software might be much easier for many organizations.