What Is A Robots.txt File & Do You Need One?
Rand Fiskin, Jim Boykin, Danny Sullivan (on Daggle), John Andrews, XMCP, Michael Martinez, Marty Weintraub were notable for the lack of a detectable Robots.txt file, so no, it appears it’s certainly not necessary to include a Robots.txt in your website, and I survived without one for long enough.
A Robots file can, simply, tell search engines certain pages of your site not to return in search results crawl. It can also save valuable bandwidth.