A ping is the only thing that happens "regular". This allows you to add some kind of bot initiated message/response.

For example, I'm running a plugin that check's a file for changes, in case the file is changed, it pushes a message into an IRC channel.

Adding this allows you to write even more of these kind of plugins. E.g. checking a server status, checking rss feeds, check for new commits on a git repo and many more.