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.
Good Luck,
mike