You're correct on that. Large scale ad spend is divided into "branding" (creating awareness about the company and products) and "performance" (leading directly

You're correct on that. Large scale ad spend is divided into "branding" (creating awareness about the company and products) and "performance" (leading directly to a sale). The performance category has many factors including the path to the actual conversion/sale and how many steps are in the way and how long it takes. It can be instant (clicking a buy button in the ad itself) or many months. Optimization is part of the process to ensure wasteful spending is reduced as analytics and sales data is generated but unfortunately the biggest issue is the people who actually run these campaigns. Lots of politics, perverse incentives, lack of skills, and general apathy.