Because that is how one says .ws!
Why would you make people say and annunciate 5 syllables for 'dot double u s', when you can have just 2 syllables to say and annunciate if your domain right of the dot is a .com, .net, or .org. ???
In my opinion, you are better off with something like FantasticFantasyFootball.com than FantasyFootball.ws! Yes, FantasyFootball.ws is shorter and all but a bear for people to remember.
Also, Sports, aren't you worried .ws might fold completely soon? Is there any assurace that the .ws registry has the resources to be here in 5 or 10 years?
Why don't you build FantasyFootball.ws, work it, and prove us all wrong. I, for one, would be happy to eat crow if you can compete well with your SomethingFantasyFootball.com competitors.