There are a lot of Civil softwares where you can specify a current object (for example, in PowerInRoads or Istram Ispol).
The current object is very very useful because it would be the default element (the selected element) in input dialog box to select it in a combobox.
If you remove the current (active) object, it doesn´t matter because then Civil 3D would work as usual until the user selects another object as active in the Tool Space.
For example, in the case of Sites, if we use the command: ParcelPropertiesEdit (Multiple parcel properties), every time you select "Sites" in the command line, the default site is the last site created. This is very annoying, because you must change it every time you want to use this command.
If you can select a site in the Tool Space as current (active) site, then this site would be selected by default for any command.