Relevance is often discussed in digital marketing. It’s an important topic because not only is it good for consumers, but it is also good for advertisers since the inception of quality score.
Advertisers with higher quality scores and relevance are typically rewarded with more traffic and lower CPCs.
The following data (indexed to allow multiple verticals and clients to be merged) proves this point. As ad relevance scores go up, CPCs go down and CTR goes up.