Not every single ad will appear on every single search. This is because the ad auction takes a variety of factors into account when determining the placement of ads on the SERP, and because not every keyword has sufficient commercial intent to justify displaying ads next to results. However, the two main factors that Google evaluates as part of the ad auction process are your maximum bid and the Quality Score of your ads.
There is limited real estate for the top positions in organic search results. With the amount of content on the web today and the number of competitors you have, it can be hard to get in a top position, even despite your best efforts. If you’re a new business or an existing one trying to build your online presence, SEM/PPC advertising can get you in front of highly targeted customers.
Although it may have changed slightly since BrightEdge published its report last year, the data still seem to hold true. Organic is simply better for delivering relevant traffic. The only channel that performs better in some capacities is paid search ads, but that is only for conversions, not overall traffic delivery (Paid Search only accounted for 10 percent of overall total traffic).