I agree - given that bit data types are packed efficiently internally, there would seem to be few instances when this technique would be useful.  IMHO the background knowledge for this is more useful for decoding SHIFT + ALT, etc, or color values in application code, rather than in storing data. 

Incidentally, there's a subtle potential bug in 'Decoding the mask - Unmask value using integer representation' - the OS's are being decoded against 3,2, and 1. In fact, they should all be decoded against 3. It's only the order in which the CASE statement is evaluated that makes this example work correctly.