It's costs server time to create a search index, as well as coding time, and even then you'll always do a worse job than google can when ranking. On a public site, adding a google custom search box is far easier and better
Which is the real question - why no custom search box on hn?
Works brilliantly. For very rare exceptions,
http://www.google.com/search?q=site%3Anews.ycombinator.com+s...