If Google just displayed links to users, then the user might actually click them, which would result in them leaving Google for another website, which is Not Okay. One of Google's largest efforts is to make sure they're the only website the user stays on, which is why they scrape contents from pages and display them on their SRP, why they want to hide the address bar from web browsers, why they push projects like AMP so hard, and many other things. Conveniently these efforts are also all of the nature that they can just claim they're helping the user get what they want more quickly - as long as they're using Google.
Users also all trust Google a considerable amount, so very few will take any additional action after being instantly supplied with an answer that is scraped from some random website. Google gets 100% of the user flow, has 100% control over what answer to show, and of course can show the user some great ads while they're at it, while denying the source website traffic for their content.