Hmm, maybe if you try to reverse engineer a file format.
If you have a binary file and you would like to find out what certain pieces mean, it could be useful.
Most likely you would better use a hex editor for that.
Another reason could be to find strange encoding errors.
For example hyphen-minus (45) and hyphen en-dash (150) look almost identical in many fonts.
If you write a program and you accidentally have an en-dash in a formula like
i=j-17; you are in trouble. I really have seen this when a colleague pasted his source code from a MS Word file into the editor. Word had converted his minus to an en-dash.
All in all it can be useful in certain circumstances, but it is nothing that I would like to have in my status line all the time.