I use it because it's nice to click a link and not have various flash videos or ads or etc. start randomly playing in the background making noise. Also, it's nice because you are able to download the video with an option in the right click context menu. Lastly, there's an option in the right click context menu to open the video in Quicktime player.
What albusseverus probably meant by "keep it pure" is that with clicktoplugin you are able to view many videos across the web using html5 instead of the default player when without clicktoplugin the html5 video option would have been unavailable to you (and only present on devices such as the iPad that lack flash player). Can you disable the flash plugin and just never use flash? Sure, but of course then it becomes a longer process when you encounter a video where flash is your only option to view. Clicktoplugin makes resorting back to flash if necessary as simple as one mouse click.
Ok, all valid points. I get it now. Thanks for the explanation.
Like everybody I wish FLASH would die, but unfortunately many streaming sites are still FLASH ONLY based. I can't watch some sports events at all on an iPhone or iPad and Safari on Macs really no longer handles FLASH well anymore.
This I why I want Firefox on iPhone/iPad.