It is currently expected behavior to only allow attributes in a query to display if selected in the Drillthrough feature. See Q&A here. It would be nice to display attributes outside of the query. Currently, it is confusing since I can select all attributes (thinking all of them will display) only come to find out that a certain number of them will. To the end user (viewer of a dashboard), that doesn't really make sense. Either limit the attributes that can be selected or allow any attribute to be selected.