The most important reason why SEO is necessary is because it makes your website more useful to both users and search engines. Although these still cannot see a web page as a human does. SEO is necessary to help search engines understand what each page is about and whether or not it is useful to users.
Now let’s give an example to see things more clearly:
We have an e-commerce dedicated to the sale of children’s books. Well, for the term “coloring drawings” there are about 673,000 monthly searches. Assuming that the first result that appears after doing a Google search gets 22% clicks ( CTR = 22%), we would get about 148,000 visits per month.
Now, how much are those 148,000 visits worth? Well, if for that term the average cost per click is €0.20, we are talking about more than €29,000/month. This only in Spain, if we have a business oriented to several countries, every hour 1.4 billion searches are carried out in the world. Of those searches, 70% of the clicks are in the organic results and 75% of the users do not reach the second page. If we take all this into account, we see that there are many clicks per month for the first result.
SEO is the best way for your users to find you through searches in which your web page is relevant. These users are looking for what you offer them. The best way to reach them is through a search engine.