People stick to default values
In The Power of Defaults, Jakob Nielsen comments on a study of how people use search engines. The study shows that people tend to click the number one result returned by a search, regardless of how relevant it is to their query. Jakob then mentions form fields as an area within user interface design where users rely on default values for instructions and guidance.
I'd say that the power of defaults extends far beyond user interface design and computers. Look at just about any aspect of life and you'll see that where there is a default, that is what most people (including myself) use, even if there are other options that actually would have made more sense.