The issue is availability of information. The further from the point of purchase you get, the more difficult it is to properly credit parts of the funnel with d

The issue is availability of information. The further from the point of purchase you get, the more difficult it is to properly credit parts of the funnel with driving purchase intent. Most analytics tools don't do a good job of crediting multiple parts of the funnel for the purchase attempt. Google Analytics, for example, can only credit one campaign per conversion event, which by default is the most recent one (it can be configured to the first one, within a time window). Engagements earlier in the funnel that drive purchase intent aren't properly credited, so they look like a less efficient place to allocate funds than the really are. The result is that resources are being allocated correctly based on the information, but the information is wrong, so as a whole the market is inefficient. Ad allocation tends to be relentlessly data-driven in optimizing, but also rather heads-down: people trust the data too much, without necessarily recognizing the flaws of the tools.