> Of course a stock image in an article is not really important and may not add much value

Not sure if anybody has mentioned this, but a super common case is that stock and other images (photos especially) require attribution. Working in the digital accessibility space, I see a huge number of examples of an image being marked as decorative (or worse, being implemented as a background image in the CSS) with an inline credit line. So as a screen reader user, I'm reading an article and keep spotting these notices all over the place, with no hint of what they accompany. In those cases, the image must have a description, even if it is thought that it doesn't add value.