Open a Shopify theme and you’ll find one og:image setting. Fill it in once, and every route on the store inherits it forever: products, collections, the about page, and the 404. Most platforms’ themes and CMS templates work the same way, which is why this is the most common failure on well-run sites.
The tags all validate. The image loads. Every checker says you’re fine. The problem only shows up in the wild, where every link you or your customers ever share wears the identical face. Liquid Death’s best-selling tallboy and its broken 404 page advertise themselves with the same card. PyPI serves one static image across half a million packages. Linktree, a company whose product is literally links, ships an asset named linktree-default.jpg.
It ships because per-page images traditionally require a design pipeline: someone has to make the assets, and nobody staffs that for a meta tag. So the default from launch week quietly becomes the permanent brand.