SEO is not just about putting a website on the first page of Google. Yes ranking matters but what happens after someone clicks is just as important. If a visitor comes to your site and cannot find the information they need, they will probably move on.
A website should be easy to understand, work properly on a phone, load well and explain the services clearly. The content should also answer the things customers actually want to know.
So, the real purpose of SEO is simple: help people find your business and make it easy for them to understand what you offer.