Why is seo so difficult?

Why is seo so hard. It seem the answer to this lies with the fact that the internet is so huge but the number of niches is so small meaning there is just a lot of competition all fighting for one place or at least 10 places available on the first page of google this means that there is a lot fo people writing and creating content for virtually all niches and search terms now to get the piece of the internet pie this is why seo is so hard. Also big company with millions of links which dont even need to bother with seo will obtain hundreds or even thousands of links each day just for half heartily writing a rubbish article which may or may not eb good which then will instantly rank in the search engines fueling more traffic and more links to them... It really is crazy so seo isn't hard... if your not a unheard of small website that is.