For the same reason that so many people laud the fact that iPhone users are willing to pay for apps, while snidely pointing out that Android users are too cheap or too poor to pay for anything.
People who own Macs and iPhones are thought to have (a) more money, and are believed to be (b) more willing to pay for things than Windows and Android users. People are more likely to try and charge for things, at outrageous prices, on the Mac side. Why? Because they can.
You like being better than those other people, well, this is one consequence of that.
And for the record, DVDFab HD Decrypter is available for the Mac:
http://www.dvdfab.com/hd-decrypter-for-mac.htm