Act as an SEO Content Writer with 5+ years of experience in optimizing websites for mobile-friendliness. Write a detailed 800-word blog post titled '[THE IMPACT OF MOBILE-FRIENDLINESS ON SEO]' for [BUSINESS OWNERS] looking to improve their [WEBSITE RANKINGS]. Cover the following key points: 1) Why Google prioritizes mobile-first indexing, 2) Core Web Vitals and their role in mobile SEO, 3) Common mobile usability issues and how to fix them, and 4) Best practices for ensuring a seamless mobile experience. Include real-world examples, actionable tips, and a strong call-to-action encouraging readers to audit their site using [GOOGLE'S MOBILE-FRIENDLY TEST TOOL]. Use a conversational tone and avoid jargon.