We crawl sites to have broad perspective how the site is structured, what are connections between pages, to estimate how much time we need to visit all pages we are interested in. Scraping is often harder to implement, but it’s an essence of data extraction. Let’s think of scraping as of covering website with sheet of paper with some rectangles cut out. We can now see only things we need, completely ignoring parts of website that are common for all pages (like navigation, footer, ads), or extraneous informations as comments or breadcrumbs.
More about differences between crawling and scrapping you find here: https://tarantoola.io/web-scraping-vs-web-crawling/
