Nathan: The comment by Mansi Rana helps answer your question. The fact is, the PageRank scores that were visible in the Google Toolbar hadn’t been updated in a long time (2+ YEARS), so they were probably getting more and more out-of-date anyway. The main reason Google would make them disappear, though, is that Google wants website owners to focus on the user and on quality content, not on trying to game the system with links.
As an Internet marketing strategy, SEO considers how search engines work, the computer programmed algorithms which dictate search engine behavior, what people search for, the actual search terms or keywords typed into search engines, and which search engines are preferred by their targeted audience. Optimizing a website may involve editing its content, adding content, doing HTML, and associated coding to both increase its relevance to specific keywords and to remove barriers to the indexing activities of search engines. Promoting a site to increase the number of backlinks, or inbound links, is another SEO tactic. By May 2015, mobile search had surpassed desktop search. In 2015, it was reported that Google is developing and promoting mobile search as a key feature within future products. In response, many brands are beginning to take a different approach to their Internet marketing strategies.