The currently viable use cases are ones that are by construction "fine" in the current privacy paradigm.

Many users simply accept whatever permission prompt they see with a shrug.

But that's partially because the only permission prompts they'll ever see (unless they're actively getting scammed) are prompts that someone thinks some users might reasonably decide to accept.

You never see a permission prompt for "send my bank details to this random other website" on a legitimate website.

There are implicit privacy constraints on what experiences are even conceivably viable.

For example, imagine a device that uses multiple cameras trained at your bed to automatically analyze your sleep, doing its processing of the video feeds in the cloud. Many people wouldn't even consider buying this product.

In that region beyond the horizon of our current paradigm, privacy matters quite a bit.

Privacy constraints are what sets the horizon of what we can reason about.

Because people are mostly fine with the status quo's privacy, we (erroneously) conclude that "people don't care about privacy."

But there are use cases that are inconceivable in this privacy paradigm, impossibly creepy, unthinkable. And those are absolutely constrained by privacy.