I searched HMVC and know what it is and its advantages.
Modularization: Reduction of dependencies between the disparate parts of the application.
Organization: Having a folder for each of the relevant triads makes for a lighter work load.
Reusability: By nature of the design it is easy to reuse nearly every piece of code.
Extendibility: Makes the application more extensible without sacrificing ease of maintenance.
But just in Codeigniter without HMVC, different sub-folders for controller and multiple model folders and multiple view folders can be created. I do not comprehend the exact reasons for using HMVC.