Right now, you can upload a personal avatar either as a Public Avatar or a Private Avatar. Some users do not want their avatars to be indexed by avatar databases, which is understandable. They may only want to share their own creations with friends without constantly sending Unity projects back and forth.
Public = Anyone can use the avatar. It can also be indexed under Section 8.3.
Private = Only the uploader can use the avatar. It cannot be indexed.
Friends Only = Only selected friends, or all friends of the uploader, can use the avatar. It cannot be indexed.
A lot of users are currently asking for blacklist or opt-out systems for avatar search services such as VRCNext Avatar Search, Prismic's Avatar Search, Avtr.zip, Cute Avatar Search, and many other avatar search worlds and websites.
Complaints toward database providers and avatar search world creators have become increasingly common because some creators do not want their public avatars to appear in these databases.
Adding a Friends Only visibility option could be a simple solution to this problem.
It could also reduce unnecessary API requests. Right now, when someone blacklists or removes an avatar from a database, multiple databases may need to re-check that avatar through the VRChat API. A proper Friends Only visibility setting could prevent those avatars from being indexed in the first place, reducing repeated requests to VRChat's API servers.