Why? As Alexey was blogging some time ago, for the dev machines and even production content delivery environments, it may make a lot of sense to disable the out-of-the-box search engine that Sitecore ships with. This may improve performance and reduce number of folders in Sitecore installation as you will be able to simply remove the whole "indexes" folder. Directions for Sitecore 6.0.x: 1.
How to completely disable Lucene index
Crawled: On March - 29 - 2009 Source