I was actually under the impression that what Pinterest does was against the ToS of Google. I can't find the link or reference, but I believe it was along the lines of 'You can't post images just to farm user account creation on your services' which is exactly what Pinterest does.
I would love if we could do away with these sites and those websites that insist I use their 'app' to view simple text data.
Pinterest is the absolute worst at this. I died a little inside when I finally gave in and made an account (using google login). But I needed to use an image for some research I was doing.
E.g. sending links to your post to friends and family. Many family members don't have accounts, and some days all they see is a login prompt. Many times, my recipient is on a different device / using a different browser / cleared their cookies because their ISP tech support somehow thinks that helps - some days, all they see is a login prompt, and don't remember their password, and don't want to go searching for it.
All of this has ensured that none of them like Instagram links, and do not want an account.
At least they're not as bad as Pinterest, which has done this for years, plus their million alternate domains polluting search results.