They want their public data public, but owned. It won’t be ‘on chain’ it will be off chain but the ownership token will be ‘on chain’.

As an example, they may have their public photos in IPFS, served from their server (or shared pointers), but will have ownership rights of those photos on chain.

That is different than Instagram where Facebook owns the images.

They cannot be deplatformed which is valuable. The question is whether it’s value exceeds the value of Instagram distribution.

Celebrities wouldn't care who owns the photos, all that matters is whether exposure leads to jobs.

The photos are valuable only to the photographer, who has the right to license it to Getty and others.

Keep in mind that you can have a "public" (doxxed) address that you use for certain activities, as well as other addresses that you use for other private activities. It can be tricky to "break the chain" between addresses if you send/receive between them, but it's entirely possible.