To explain why Core Web Vitals are important take this problem for example, have you ever tried to click a button that doesn't work and then after a couple seconds it does start to work? That is an example of a sort of input delay kind of problem with users. Google doesn't like this. Google wants the best page experience for all of their users. These loading issues and other problems like cumulative layout shift which describes when pages start to load and you start to see things on the screen but they haven't settled and if you click something there is a sudden shift away. Google is measuring the time it takes for that page to become stable as part of their Core Web Vitals. This and other user experience problems that Google has identified with websites and given these names to given scores to, is why Core Web Vitals are important, they will affect your rankings.