Why Should we use Resource Files in defining UIs ?

Symbian (and its Licensees S60 and UIQ) provides a lot of the infrastructure for an application in Symbian.C++ that is already prebuilt[like MFC] so it is not really practical to reinvent the wheel with more code to rebuild the controls.

Additionally to provide a consistent framework across devices, the underlying OS uses a framework calls LAF which dictates how controls should look and where they should be on the screen so that there is a common style to all applications.

Also Keeping source code and resource files separate, which gives lots of advantages
1. easy localization,
2. developer only need to recompile resource files if there are any changes in the UI elements.