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)....