Why can't data recovery programs for domestic PC/Macs recover all file types?

I have a Mac. I have overwritten a folder with some files with the extension 'exs', which map samples over a keyboard for a music interface called Logic. I am desperately trying to recover these files using data recovery programs, but all they seem to be able to find is Jpegs, Mpeg and all other common file types. When they search a drive they don't seem to list every single file type. Why can data recovery programs recover lost movies and images but not specialised file types? Is there a data recovery program that can retrieve specialised file types?? Many thanks