The QWERTY keyboard has been around since the late 1800s. It is still the dominant format for most keyboards, now primarily seen on desktop computers, laptops, netbooks, and smartphones. Although the QWERTY was somewhat intuitively designed, by placing letters in different positions based on frequency of usage, it is not considered the most optimal model for a writing interface.
So why does QWERTY still dominate? It is still by far the most popular format because of the self-reinforcing cycle of usage-and-training - i.e. because QWERTY is so universal most new typists learn to type on QWERTY and thus demand it in the future, this makes QWERTY even more universal. The same cycle can be seen in hundreds of examples every day: the steering system for cars, the computer mouse, the telephone, etc.
For a new system to replace the old and well established way of doing things, it needs to be more than just better. It must be so much better that it breaks the usage-and-training cycle. This is clearly a tall order but also a very lucrative opportunity. That's why so much money continues to be spent (wasted?) on improving technologies such as voice-recognition and touch-screens. The value of becoming the new universal standard is enormous.