Relational databases got advanced enough (with recursive CTE's in SQL, and soon with the newly standardized Property Graph Query, which adds a much welcome bit of syntactic sugar) that there's just no point to a general purpose graph DB - plain old RDBMS can serve that use case just as well. "Graph" based systems might still be useful for doing highly advanced, math-based network analysis on large sets of data, but that's a very different thing.