Why are impression-based metrics alone insufficient for evaluating a new ad copy's potential effectiveness?

Impression-based metrics alone, such as the number of times an ad is displayed, are insufficient for evaluating a new ad copy's potential effectiveness because they only measure visibility, not engagement or conversion. Impressions indicate how often an ad is shown, but they don't reveal whether users find the ad compelling, relevant, or persuasive enough to take action. An ad can have a high number of impressions but a low click-through rate (CTR) if the ad copy is not appealing or doesn't resonate with the target audience. Furthermore, even if the ad generates clicks, a high number of impressions without a corresponding increase in conversions suggests that the ad copy is attracting the wrong type of traffic, or that the landing page is not aligned with the ad's message. To accurately evaluate ad copy effectiveness, it's essential to consider metrics that reflect user engagement and conversion, such as click-through rate (CTR), conversion rate, cost per acquisition (CPA), and return on ad spend (ROAS). These metrics provide a more comprehensive understanding of how the ad copy is performing in terms of driving traffic and generating desired outcomes. For example, an ad with a low CTR but a high conversion rate might be targeting a very specific and qualified audience, while an ad with a high CTR but a low conversion rate might be attracting unqualified traffic. Therefore, relying solely on impressions provides an incomplete and potentially misleading picture of ad copy performance.