Why are American writers not winning Nobel prizes anymore?

For almost nineteen years no American writer has been awarded a Nobel prize in Literature (the last one was Toni Morrison in 1993). This is a somewhat unsettling figure if we consider that the United States has traditionally being home of great writers such as William Faulkner, Ernest Hemingway or Isaac Bashevis Singer. 

Is it that we are witnessing a declination of the literature of The United States? It is not that there is a lack of writers who tell great stories. As an example we have Stephen King and Stephanie Meyers who have amazing stories to tell and easily sell thousands of books (meaning also that there are still many avid readers waiting for a good story to put their hands on). However, it's also true that though their books are best sellers that does not mean they are great examples of literature. They offer a good reading. That's all.

There are of course gifted writers out there, but they are doing something else, not necessarily writing good books. They could potentially beat any competition (literary of course), but they are not winning anything for a reason I dare to venture: they are all working for movie or TV companies. They are the ones who write for acclaimed TV series such as Lost, Friends, or Smallville or writing great scripts of movies such as The Artist or Inception. The great American writers have not gone anywhere but the power of money seems to have won them over and alas they are not producing true literary works. 
Is this good or bad? Well, if you enjoy going to the movies and see productions such as The King's Speech or The Help, or watching those outstanding series such as The Tudors or Glee then it's good. If you consider yourself a reader of only real literature, one at the level of John Steinbeck, then you sorely miss the waste of all that talent. In the end, there are no regrets and as long as their wallets are fat, those writers are not devoting their talent to anything else but "our entertainment".
Who wouldn't?