What makes it worthwhile providing metadata?
The fact that companies like Google and Microsoft provide this metadata also themselves? Or the fact that these companies make use of the metadata you provide?
The Schema.org sponsor’s search engines provide no (Bing, Yahoo, Yandex) to little (Google) metadata using the Schema.org vocabulary, and this might have various reasons (for example, they might not like/allow that some other party/tool parses their SERPs, so why make it easier?), but none of their reasons should stop you providing it. Big company websites rarely serve as good examples for HTML best practices.
So you just have to decide: Do I want to enable humans and machines to make better use of my content by providing metadata? Your answer should not depend on who else is doing it, but on who is consuming it.
And as a side note: If you want to find out if a webpage is using the Schema.org vocabulary, searching for "itemt" and "itemp" is not sufficient. This would give results if the Microdata syntax is used, but there are other syntaxes for making use of vocabularies like Schema.org, e.g. RDFa, JSON-LD, Turtle etc.