I have put up with this discrimination for years, as sharing with strangers does not work for me.\
To rub salt into the wound, if you notice in a lot of the adverts, the prices for cabins are noted as Per Person,then when there is an "On Board Credit" it states SINGLE CABINS 50% even though you are paying for TWO. I have tried and tried to get answers to all of this, however Travel Agents (who are usually of the younger generation and cannot understand why anyone would want to or have no choice to travel alone)
Some Cruise Lines say they have a no single supplement, usually the very expensive River Cruise Companies, and the prices are just out of normal people's range.
I also get annoyed at the "Single Supplement" tag, its not a Supplement, to people that means you would just pay a few dollars extra.
No wonder people take other holiday options. However I just love cruising, and save hard for the joy!!