What title are you referring to? I am guessing that title got edited and initially used partial header from github page "A Hex Editor for Reverse Engineers" cutting of second part "Programmers and people who value their retinas when working at 3 AM".
Hex editor can also be very useful for programmers when working with binary file formats. Implementing support for image and archive formats. Testing that your code outputs the thing you expected it to output or inspecting a file which your program fails to process because some other program included some unexpected option fields or something like that. It's sometimes even useful even when working with text fails, typically because they included some invisible symbols which you didn't expect or differentiating between similar looking unicode symbols.
Hex editor can also be very useful for programmers when working with binary file formats. Implementing support for image and archive formats. Testing that your code outputs the thing you expected it to output or inspecting a file which your program fails to process because some other program included some unexpected option fields or something like that. It's sometimes even useful even when working with text fails, typically because they included some invisible symbols which you didn't expect or differentiating between similar looking unicode symbols.