In any market, the share of people ready to buy right now is small. The large remaining segment hasn't yet defined their problem, or hasn't started looking for a solution. A strategy that plays only to the ready segment pushes CAC up as competition intensifies in a narrow pool.
Creating and capturing are different jobs
Demand capture (SEM, retargeting, outbound) harvests existing intent. Demand creation (content, brand, organic and paid social) builds intent in the segment that isn't yet a buyer. The two are measured by different metrics and operate on different time horizons; substituting one for the other caps growth.
A single CAC/LTV logic
When channels are optimized independently, the contribution of creation activity to capture performance becomes invisible. The right setup ties channels together in a single CAC/LTV framework, making the effect of brand on search volume and content on conversion rate readable.