The main task of a search engine is to give a high-quality answer to a user’s request. That is, choose the most relevant, convenient, informative, authoritative among the many sites. So, for example, search engines take into account when ranking:

page loading speed – the faster it loads, the better the position in the search (all other things being equal);
adaptability – ease of display in all devices, browsers, operating systems;
site security – the presence of connected https, the absence of viruses;
coincidence of words from the request with meta tags (title, description), since they contain additional information about the page for search engines;
availability of reviews, information about payment, delivery, guarantees.
Thus, when you do a smart SEO optimization, you not only increase traffic to the site, but also improve the user experience in parallel. Convenience and informational content give the visitor a reason to stay on the site longer, come back more and more, place orders, leave applications.