Improving ad relevance is well worth the effort since it results in an overall campaign improvement-higher quality score, better ad position, and lower cost-per-click.
Inshort, higher ad relevance = higher quality score = lower cost-per-click.
On both Google and Bing. Quality score is partly measured by relevance.
Ad relevance can mean a lower CPC and higher ROAS which is what every digital market wants. This is because higher relevancy can lead to a better position on the results page. Naturally, with more visibility, this earns advertisers more clicks for the same budget and a lower CPC. Think of it this way: higher ad relevance= higher Quality score= lower cost-per-click.