You are certainly free to move the plumbing fixtures when you remodel your bathroom. The reason for not moving the fixtures is to reduce the cost of your remodel.

Moving plumbing fixtures in a bathroom requires a good bit of work, which produces high labor costs on the project. You can save a good bit of money by leaving plumbing fixtures in the same place, even if you turn them in a different direction.

Moving plumbing fixtures will require changes to the floor and subfloor, moving pipes, changing pipe joints and connections, and could involve tearing out ceilings and walls beside and/or below the bathroom in order to gain access to existing pipes. To find out exactly what the cost difference will be, ask your plumber for an estimate. Bathroom Remodeling Workbook by Dan Fritschen