Because the search is a very complicated thing. Think about what you are asking. You need a tiny search engine that can simply determine how your spreadsheets are laid out, and what are relevant and what things need to be done. If you can come up with this, you will be rich and probably work for Google.
Lucene, as you mentioned, or the Sphinx search ( http://sphinxsearch.com/ ) are great. MySQL also has built-in full-text search, which you can find at http://dev.mysql.com/doc/refman/5.1/en/fulltext-search.html
But they all take configuration and implementation. They are not just going to “know” what you want.
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