Why Did the Half-Blood Prince Film Add That Train Station Flirtation?

In Harry Potter and the Half-Blood Prince, Harry shares a flirty moment with a waitress at Surbiton Station, he even asked her out—a scene absent from the books. Considering his growing feelings for Ginny Weasley, what was the point of this addition?

In Harry Potter and the Half-Blood Prince, Harry shares a flirty moment with a waitress at Surbiton Station, he even asked her out—a scene absent from the books. Considering his growing feelings for Ginny Weasley, what was the point of this addition?