Robots.txt, is it needed?

Just wondering, with vbseo and the sitemap installed, is there a reason to have a robots.txt? Like, are they in any way helpful?

It's a good idea if you need or want to block stuff from bots without making the area private.

ie, search.php, usercp.php... bots will never index or use these pages, but there's no point to making them private, so to save the bot some time and to let it focus on your important areas, its nice to block those areas.