Social networks are challenging.
By nature of the service you have to sign up with a lot of personal information. If you don’t it’s hard for people to connect with you in anyway.
The other challenge is that unlike search Social Networks don’t have a keyword that you are searching, which is an easy way to give you relevant advertisements without tracking.
This means a privacy focused search engine would need to show random ads to users which would likely be fairly low quality.
It’s a complicated problem to solve, but, I hope someone is working on it!