Single Supplements for Cruising

Is it me or are there a lot of Cruise Lines that are charging high single supplements for single occupants? I have recently seen some Cruise Lines charging 100% single supplements. Is this fare?, or is this just the way Cruise Lines operate to maintain the full occupant cost, not losing out on business.

I can appreciate that Cruise Lines need to make up their business and do not want to make a loss on any cabins booked. However if MSC can do a 0% single supplement on some of their cruises why can’t other Cruise Lines follow suit.

Recently I have booked single customers on to MSC cruises and the cost has been incredible. No single supplements, same benefits as other cruises including free “cheers” drinks package. Single travelers at the best of times can’t afford to be paying double for their cruise. So can other Cruise Lines be offering lower or if not 0% supplements on some of their cruises? Even if they just allocated a small % of cabins for single travelers at a reduced rate!