In plan view, by default the columns 'Duration', 'Start date', 'End date', 'Estimated', 'Reported' and 'Remaining' are displayed.
We don't used time bookings to the last three columns 'Estimated', 'Reported' and 'Remaining' are just white space occupying screen width. It seems to be an option to move the vertical bar between the left side columns and the Gantt view to the left but this will cause the first column with activity names getting useless small (cutting activity names are hiding them at all).
The best solution would be to provide an option to hide columns in plan view to get more space for what is important. Another option would be to set a minimum width for the name column to that moving the vertical bar can be used to hide columns starting from the last one.