Web Standards and its disregard by all major search engines?

I'm a big fan of that little icon which you stick on your website 'To show your readers that you've taken the care to create an interoperable Web page, you may display this icon on any page that validates.'. (Do a Google search you'll find it fine!). My main question is if we're all supposed to follow this (and I've been advised on many occasions it helps with search engine optimisation) then why the hell do the major search engines not bother to follow more or less ANY of these standards?

I checked Google, Yahoo, AOL, Ask. None of these search engines follow web design standards?

Is it because the search engines don't need to be found?