Google is a hundred-billion dollar company precisely because it allows advertisers to see how effective their cost per sale (or action) is, compared to TV or newspapers, where advertisers are flying blind.
Measuring the effectiveness of brand advertising on YouTube is more difficult that measuring TV/newspapers. TV and newspapers have higher repetition at an individual consumer level so the "which newspapers do you read?" or "which programs do you watch?" survey questions work. Additionally TV and newspapers have older audiences who are both more tolerant to ads and susceptible to brand advertising. YouTube is not particularly effective for CPA advertising so the technologies from other Google ad products are not that relevant.
This is actually untrue. Have you ever seen a survey in a YouTube ad, asking a question like "have you ever heard of Brand Z?" That's one of several mechanisms for measuring brand awareness lift, seeing the lift in recall over a control group.
Likewise, many advertisers aren't doing brand campaigns, they're doing direct response, that is, trying to get people to directly click to their site and convert.
Finally, advertisers on video sites tend to pay per "completed view" for some definition of completed view, usually at least a significant chunk of the video and not just the first few seconds before the skip button appears.
Why would you need a survey question to track YouTube habits? Google already has that data, why wouldn't they just correlate that to a future purchase you make?
Statistically reliable purchases studies are very challenging. People have multiple credit cards and sometimes pay cash. If you are buying a car you don't put it on the credit card. Additionally, you have multiple cookies/MAIDS that may or may not be associate with the same person/credit card. Even companies with Google or Facebook resources can't get this to work reliably. If it is a direct response advertiser, of course, you tell Google/Facebook that a purchase is made, but these advertisers are not the bulk of the market and many advertisers don't want to give Google that data.
