There are valid reasons to restrict the visibility of your content to registered users.

I post nudes on a certain site, where I have the ability to choose who can see my pictures. The options are: everyone, friends, registered users, and VIP members (paid subscription). Nearly all of my pictures are set to be visible only to registered users, with the spicier ones restricted to VIP members. My reason for this has nothing to do with trying to force people to create an account, let alone pay for a subscription. I have no illusions about my content being completely safe from outsiders. I simply want to create a small amount of friction to prevent complete randoms from easily accessing my content when they have no personal investment in the site. I see putting myself out there as the price I pay for free access to everyone else’s profiles. If you want to see my pictures, I expect you to do the same. I’m taking the risk of potentially being recognized - I expect you to take that risk too.