Once you’re at a certain marketing spend, more targeted advertising has diminishing returns — you’ve already targeted your existing audience and converted the ones that are ready to convert.

In addition to helping your existing targets convert due to an increase in brand trust, broad based advertising also helps you break out of that local maxima by delivering new customers that are unlike your current target. You can then identify new segments of customers, interview them to understand their unique use cases, and build targeted campaigns for those new segments.

Measuring this and executing on it is an order of magnitude harder than just running targeted ads, because the conversion effects are distributed across all of your campaigns and the timelines are much longer. However, most any sophisticated marketing team will develop these types of campaigns once they start seeing the effectiveness of targeted advertising start to decline.