Users of the web site are constantly looking for something in search engines. They are your clients in the future.
This kind of search is done by the thousands a day. But users may not find your site. Because you don't have search engine optimization. But the appearance of your site in the TOP-10 of Google or Yandex is already SEO promotion on the Internet.
For example, if you search on Google for "buy a profile" or "dentist in Tashkent", you immediately click on the first site as a result of the search. As a result of SEO, website traffic increases and you get more calls, more orders and, of course, more profits.