Hey! So, if you're wondering why mobile optimization is such a massive deal for SEO right now, it honestly comes down to how both users and Google actually behave these days.
Speaking from experience managing the SEO and analytics for a few different sites over the last couple of years, usually around 60% to 70% of all traffic comes straight from smartphones. If your mobile site is clunky, slow, or hard to navigate, people are going to bounce immediately. High bounce rates and low engagement times send a huge red flag to search engines that your page isn't providing a good user experience.
But the biggest technical reason is Google’s Mobile-First Indexing. A few years back, Google completely flipped their algorithm. Now, their crawlers look almost exclusively at the mobile version of your site to determine how to rank you—even for people who are searching on a desktop! If your mobile site is just an afterthought (like if the text is too small, links are too close together to tap, or the load time is terrible on a standard cell network), Google will tank your rankings across the board.
If you're looking to improve things, I highly recommend running your URLs through Google's PageSpeed Insights and focusing heavily on your Core Web Vitals. Make sure your images are compressed and your layout doesn't shift around while it's loading (Cumulative Layout Shift). Trust me, optimize for the phone first, and your desktop rankings will naturally take care of themselves.