Rose has been making observations, people-watching, and doing all the sorts of things she could imagine the Doctor doing in a time like this.

The last bit she feels she needs to do is - well, find out more about this place. Bartenders, in her experience, tend to be pretty reliable when it comes to information.

So that is why Rose has approached the bar.

"'llo, I don't suppose you've got any drinks from Earth, do you?"