Why not?
Because it is non-standard and specific to one search engine only -- its like tailoring html to one browser only -- not good :)
It's easy to do and should only take the site maintainer a couple of minutes.
While this helps, it really has never been important consideration
It will help users get better (more relevant) Google search results.
Very doubtful
If you fear we will end up adding specific codes for dozens of search engines, that fear is unfounded. Google is 70% of the search market share, so adding just the code for Google we'll get most of the gain.
Take it as political advocacy, forget google :)
From what I see, the googleon/googleoff tag was introduced since 2009 so it's quite mature.
googleon is fundamentally immature
google has been indexing perlmonks a decade before; Super Search is even older. PerlMonks has had comments in html source that whole time. If google wanted to do something about it they had all these years.
Noindex claims Googlebot doesn't support googleon/googlef , says its a feature of the hardware Google Search Appliance, in other words , google doesn't want you to add these tags to the internet
Even if Google decides to ignore the tag, the tag is a normal HTML comment tag so it won't do any rendering harm.
:) comments, they're supposed to help devs/maintainers, not search engines
But seeing how googlebot/google will ignore them, since this feature is for owners of GooSeaApp (devs), it won't help us