A page that cannot be crawled does not exist as far as search is concerned, however good it is. Crawlability fails in quiet ways: a robots.txt rule, a bot protection page served to identified crawlers, a login wall, content that only appears after JavaScript the crawler does not run, or a link graph where the page is never linked from anywhere.
It is the first thing a technical audit checks because nothing else matters until it passes. Our free audit fetches the page the way a crawler does and reports what it could and could not read.