First point is that many SEO's are coming out every year and they compete each other with their client competitor sites. This increases the level of total competition.
Second is that the frequent industry updates in organic promotion. SEO beginners and intermediates need to update their knowledge by reading top sites like Search Engine Watch, Search Engine Land, Google webmaster help and many. Subscribing to Google blog will as well support.
Earlier, old SEO's had very minimum options to learn and practice with the help of forums and very minimum number of experts articles and understanding the algorithms tactic was not so easy like now. And the only advantage was that there were minimum SEO's, so with basic knowledge many SEO's were able to survive in the industry.
But now the algorithm is more open and we can see many free advices from top SEO experts on most of the tactics that has been gained through years of experience like the free advice articles section you see here.
If you want to win the game in organic listing, it is not only defeating your client business competitor online, it also includes your SEO knowledge updates compared to the SEO's who promotes your client competitors sites that helps you to maintain the results.
So in order to get good SEO results and to be effective in the SEO competition, you need to be updated with the current SEO trends and examine what you learn through various forms. Drop your comments if you need more insight.