... the US Department of Justice decides to reach beyond its own borders to crack down on internet gaming. After sneaking anti-gaming law into "port security" legislation last year, they're now getting serious about enforcing it. Companies (most of them offshore) are losing a ton of their value in the market and many big names have pulled out of the US.
So poker (where a player can control the outcome to some degree) is out, while horse racing and lotteries are still in. Makes perfect sense.
Disclaimer The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way, shape, or form. Seriously.