A copywriting approach to advertising whose format is to state a fact about a product or service in a headline and then explain why the fact is true in the copy text. The idea behind this type of advertising approach is to give a reason why a customer should buy the product or service. Reason-why advertising works better in long copy and long-form ads (including infomercials) than in short-form broadcast, because the prospect has more time to consider the message.
Broadcast presents a time limitation, and the viewer may very well miss the opening headline or the reasons why the opening headline is true.
Synonyms: reason-why copy