By default you can't copy and paste images from clipboard to text field using CKeditor, I would argue this should even be in core as if you are writing an article this would be very useful to have, even more then what "Media" module brings. So how to add this to drupal. Well not easy as usual :)
To add this you need a CKEditor plugin that can be found and tested here
and module to add this for drupal is here
It adds few CKEditor libraries to make this possible, but once they are installed and this module is Enabled it will run out of the box in your CKEditor, creating image files in your public files directory.
Example of copy paste from clipboard