* Famous to whom? The question is subjective. Everyone knows her name, but does she have a specific connection to D.C.?
* Washington's population: Washington, D.C. is a large and diverse city. While most people would recognize Julia Roberts, not everyone would necessarily be interested in celebrity culture.
* Political focus: Washington, D.C. is a politically charged city, and celebrities often take a back seat to political figures.
So, while Julia Roberts is undoubtedly a globally recognized star, her fame might not be the primary focus of attention in Washington, D.C. compared to other cities.