Some changes happen rapidly while others flow and ebb with glacial speed. As we enter 2008, one of the standard predictions is that this year is the demise of carrier portal domination and the rise of off-carrier deck sites and free choice. It would sound promising, except that this claim has been raised for each of the last 5 years.
Certainly, you can find games off-portal. Over 1.25 million free mobile phone games are downloaded each month from MobileRated, a leading off-carrier deck mobile entertainment site. Other companies are moderately successful selling games directly, but their revenues are dwarfed by that obtained on the carrier decks. The reasons remain the same too.