Just did a Google image search and I got hundreds of images. A large number of them came from pInterest. When you click on the link, you're required to either log into the site or use their app before you can look at the content. This also happens when using text searching.
Meanwhile, I'm developing a site for a client and Google Search Console is flagging all kinds of issues it's finding with mobile friendliness, such as wether the page requires too much scrolling, button placement, etc. The site is actually usable.
I can't fathom how a site that obstructs visitors from merely seeing their content unless they log in or run an app is considered mobile friendly. It is more puzzling that the content is mostly user generated links to other public sites. Why can't Google present those links directly? Is this web payola or some other reason?