James Surowiecki has written a nice article Feature Presentation about why companies build complexity into their products and more importantly to you--why you buy into it. People want all the bells and whistles but overestimate their ability to use all the features. The challenge is to make complex things simple.
The fluent UI in Office 2007 is a good example of how MS is attempting to make complex things simple. Sometimes a better user experience it isn't about creating new features but rather retuning existing features to be more intuitive and easier to use.