Don't quote me on this, but since a) most of the WW casinos are licensed in Alderney, and b) a clause in the WW contract with the operator BOTH prevent US players from playing the games in real, WW (and possibly Alderney) may be telling them to pull the plug from free play as well....
I hypothesize 2 reasons:
1. People are getting bored with the same old MG,
RTG and others who seem to introduce clone afer clone time after time and people want to play the games they are familiar with in a true B&M casino, so WW/IGT is saying "OK... you wanna play these games? Then go to a B&M!"
2. Alderney sees that since the UIGEA is supposed to combat all forms of wagering, they may see it is actual money play (even though it actually isn't - it falls within the bounds of free play as specified by the UIGEA), and they tell the ops to pull the plug. I see them getting a huge backlash with this one if it happens to be the case.
Who knows? Maybe they just want to tell Americans there are better places to play? Any casino that excludes one group from another is essentially telling them "We don't want your business because we're scared of what could happen to our profits." Sorry if that's a lil' ruthless, but IMHO it's the truth.
And BTW - I can still play for free at GamesXtra.