Google and Bing have algorithms that decide the universal result on the SERP.  Bing calls their algorithm the Whole Page Algorithm. Google is more secretive about the name of its algorithm. In 2022, John Mueller irreverently referred to it as “The Super Search Engine,” Gary Illyes used the term “Universal Mixer.” They confirmed a Whole Page Algorithm exists at Google.
The Whole Page Algorithm decides which Rich Elements are embedded in the blue links. The Whole Page Algorithm is presented with the candidate set from each vertical in the search engine index: Blue links, videos, featured snippets, images, related searches, podcasts, etc., and it builds the best SERP based on the user query and intent.
Nathan Chalmers, Program Manager, Search Relevance Team at Bing, told Jason that click-through isn’t used in the algorithms that create rankings. The click-through rate is critical to evaluating the Whole Page Algorithm: how users interact with the search results is crucial to how Bing measures the success of its product.
At Bing, this user behavior is fed back to Darwin. Darwin is an algorithm within the Whole Page Algorithm with the authority to veto or change any results the other algorithms suggest. After humans interact with Bing search results, Bing staff feed Darwin corrective or reinforcement data to improve performance. So, although Google has insisted that the click-through rate doesn’t affect rankings in the core algorithms, user interaction on the SERP (including click-through rate) does impact whether potential Rich Element candidates appear on the first page of the SERP. Click-through rates affect the layout and design of the SERP. User interaction with the SERP is fundamental in SEO.
Google has not confirmed whether the Whole Page Algorithm has any similar veto algorithm. Google is a commercial product, making a veto algorithm essential.
Pro Tip: The aim of the SERP is to give the user the best solution to their question as efficiently as possible.