The only reason it works is because these youtubers know that the largest demographic on YT is 8-22 year olds who are immature. On the flip side, the advertisers think they're advertising to adults with disposable income....thus it because a huge waste of ad spend for the advertisers but they haven't realized that yet. All they know is TV viewership is decreasing and online media is rising...so they need to do something to push their products.
Well they are advertising to people with disposable income, by proxy: the parents of the kids who watch the videos then beg/nag their parents for things from the adverts.
