Whenever you first learned AutoCAD, there's a good chance at least some portion of the class/book included a discussion about the Cartesian coordinate system used throughout AutoCAD. I'll spare you the details, but to summarize coordinates help us identify the precise location of objects in our drawings. While I would argue coordinates are important for any design discipline, there is perhaps no discipline where coordinates are more critical than civil engineering. Since the x- and y-coordinates represent the precise Easting and Northing location on a project site, knowing where you are on a project site is a critical bit of information.
Ever since I started using AutoCAD with release 12 for MS-DOS, the coordinate readout has been in the lower-left corner of the Status Bar. In an attempt to save screen real estate, AutoCAD 2015 combined the Layout tab interface with the Status Bar interface. I'm not quite sure why, but the default composition of the interface omits the coordinate readout from the Status Bar.
While I cannot answer the question of why this was omitted from the default interface, I can answer the question of how to add it (back) to the interface. The secret is to click the Customize button (three horizontal lines) located on the far-right side of the Status Bar. Choosing that button will open a menu where you can select Coordinates.
Adding the coordinate readout is as simple as that. As soon as you choose Coordinates from the Customize menu, the coordinate readout is added to the far-right side of the Status bar.