aka Filler: Filler is material of lower cost or quality that is used to fill a certain television time slot or physical medium, such as a music album. https://en.wikipedia.org/wiki/Filler_(media)
Most advertisers don't want to be in a publication that has no "independent" content. So publications actually have targets for the % mix between editorial-content and advertising.
Without this, the PR industry might not exist.
During the DotCom bubble, tech mags found huge increase in advertising demand. So they had to increase the quantity of "news" to put between the ads. Did quality suffer?