Quote Originally Posted by ebrian View Post
And yet the pages you posted made no mention of rebuilding an index

Since the OP's question was in regards to rebuilding indexes and not the low-level mathematic algorithms or science behind indexes, careful reading of the doc does mention that rebuilds are beneficial under certain circumstances.

Nevertheless, even if the doc was 10066 pages, sometimes it is still impossible to dispel the myths that are inevitably perpetuated as evidenced by Gitesh's comment above.
If you understand what a basic binary search tree is, and how performance can improve with the use of self balancing trees, you might realize that with a btree index, the index will end up in the most efficient state. Instead of thinking about indexes as a black box where you have no idea about the implementation, having a full understanding of the inner workings of the index will help dispel the index rebuilding myths that have perpetuated so much over the years. So yes, look at the underlying data structure.