Who wants to write code for some exotic chip that's only used on one gaming platform? If I'm not mistaken, making effective use of the cell processor requires you to manage the cache by hand. This is the kind of totally unportable feature that requires expert treatment and lots of fine tweaking.

Now, instead, you get 8 x86 cores, with multithreading, and quite probably a GPU you can also use for general purpose computation if you want to. Simplicity is going to be an advantage.