Still today, a BIG fraction of the pages that get accessed are SEO optimized pages.
This strategy worked better actually around 2 to 3 years ago.
Now, it is possible to optimize pages relatively easily but it is getting serach engines to index them that is the challenge.
Right now, only around 40% of the site is actually indexed and shows up in search engines.
The other pages have been crawled but not indexed even when a site map is submitted