A free text search on your content via a search input is the killer app of a search engine but it is not the only app of a search engine.
A search engine (and its backing index), just like a relational database, is a technology that allows you to build all sorts of solutions on top of it. Nobody says don't use a graph db because Facebook already has the best friend of a friend solution you could hope to find.
Yeah. Absolutely. There's plenty of merits in the pursuit.
But products are constrained by requirements and most of the time the manager thought search was in there, after a little talk, search was not in there any more.
There's resources, deadlines, budgets, contracts to satisfy, blah blah blah. The insight is this costly feature can usually be shaved from the requirements with a little conversation.
A big secret of "10x" programming is realizing "90%" of the work isn't truly necessary.
But yes, search is totally a fantastic thing to do if you have the space and expertise to do it.
A search engine (and its backing index), just like a relational database, is a technology that allows you to build all sorts of solutions on top of it. Nobody says don't use a graph db because Facebook already has the best friend of a friend solution you could hope to find.