This is such a vital option and has cost me several times because its buried in the settings.
Surely whether or not your site is being indexed is of far greater importance than most items that are currently visible on the dashboard.
While developing a new site on beta url I always check the box to "discourage" search engines. It is natural to go thru every setting while building site. But not so much post launch.
There should be a giant button on dash alerting you to current status of robots.txt or "discouraging search engines."