Google uses theirs (.google, .goog, .gle, .youtube) both for public and infrastructure stuff. Same with AWS (.aws).
For things like `pki.goog` or `ecr.aws` I think it makes a lot of sense; compared to an equivalent .com domain it removes the Verisign dependency from the DNS resolution chain.
They are rarely seen, as many consumers don't identify them as domains. People understand the meaning of "example.com" in an ad or something. Thus companies are reluctant to put their primary site to not established TLDs.
Companies also always "need" the .com (and country, TLD) as people will always try companyname.com.
New TLDs work for some people's blogs, some places with more technical audience or specific marketing campaigns.
