Let me first give you a scenario in which this option is convenient. Say you have a page that continuously get minor updates that need to be published immediately. But you want to prepare a new version to be published in a couple of weeks. What do you do? Creating a new version that is not approved is an option but can fail sometimes. Luckily there is another option: change the page restrictions!
In the Content Editor on the Publish tab there is an option called Change.
If you click it you will see a list of versions with checkboxes that set the publish behavior for the page per version! So if you uncheck your version that needs to be published in the future, you can happily prepare you page without concerning workflow states, etc.
In the meantime you can keep changing the ‘older’ version and publish the whole page. I bet you did not knew this feature exists in Sitecore!