Like all the other organs alleged to be vestigial

The Vestigial Organ Deception Has Once Again Been
Refuted By Scientists

According to research findings published in the journal Evolutionary Biology, it has now been announced that the appendix, described by Darwin as an organ that had become vestigial during the evolutionary process, in fact performs important functions and Darwin made that suggestion based on ignorance and a lack of scientific knowledge.

Darwin imagined that the appendix had no function in the body. He therefore claimed that it was an evolutionary remnant since the organ had not been used in the process of evolution. Yet contemporary scientists have now refuted this claim of Darwin's.

A team made up of researchers from Duke, Arizona and Arizona state universities discovered that the appendix safely harbors good bacteria, and that these do not leave it until required.