Google has one main aim: to make money by providing its users with a superior product.
A large part of what Google is about is delivering search results that best provide its users the content they are looking for. A simple of measure of whether this is working out is how long the searcher spends on a site having visited it from Google’s search results. If visits are short, it is likely, but not definitely so, that the site is not what they wanted to see.
The overall quality of the whole search experience reflects on Google’s brand image so if you repeatedly end up on sites you don’t like, that will reflect badly on Google. So Google is keen that you get a good experience from the sites you visit. This in turn requires that the sites deliver what you want in a style you like. One way to aid this process is to help website owners improve how visitors react to their sites. Google’s Optimize system aims to do this in a relatively easy way.