Building links is an important aspect of search engine optimization (SEO) because it helps improve a website's visibility and credibility. When other websites link to a particular site, it signals to search engines that the linked site is trustworthy and relevant. This can result in higher search engine rankings and increased organic traffic. Additionally, building links helps to establish relationships with other websites and expand a site's online presence. Therefore, it is necessary to build links in order to keep up with the competition and stay relevant in the digital landscape.