To know why Adsense is essential for your content sites is to know first how this works. The search engine is the one handling all the tracking and payments, providing an easy way for webmasters to display content-sensitive and targeted ads without having the hassle to solicit advertisers, collect funds, monitor the clicks and statistics which could be a time-consuming task in itself. It seems that there is never a shortage of advertisers in the program from which the search engine pulls the Adsense ads. Also webmasters are less concerned by the lack of information search engines are providing and are more focused in making cash from these search engines.