So, the reasons we don’t have widespread graph support:

• There are many different kinds of graphs
• There are many different representations of each kind of graph
• There are many different graph algorithms
• Graph algorithm performance is very sensitive to graph representation and implementation details

Hillel Wayne

The Hunt for the Missing Data Type

Source

This means you, as a developer, need to understand graphs and how to build your own representation of them - one that fits the problem you are trying to solve.