Why doesn't Java provide a Graph interface or class implementation in the core API?

Why doesn't Java provide a Graph interface or class implementation in the
core API?

I'm trying to understand why Java doesn't provide a basic Graph interface
and/or Class implementation in the core API?
There are certainly many subtle differences in how graphs can be used and
implemented, but providing a basic interface and default implementation
for the base cases (directional vs non-directional, weighted vs
non-weighted, sparse vs dense) seems very sensible as this data structure
is becoming commonly used.