They are taking the data from the scans and building a nice easy to use searchable signature database for script kiddie hackers. At the very least, it's impolite.

If they know what software you are running, the minute there is a new vulnerability revealed, they can break into your system. It gives you less time to patch your stuff. You think this is the stuff of fantasy? Read https://www.drupal.org/PSA-2014-003