> It seems to provide a universal and sensible offer to members of the public: "I am happy to be advertised to for a small fee".

Generally, you are provided a sensible offer: You can use many games, search engines, communication platforms, and other internet services for free. Those tools cost a lot of money to build and maintain, and you don't pay anything.

Also, I have seen products pretty similar to what you suggest. There have been apps and websites that promise you gift cards in exchange for watching ads. Basically trying to increase Adsense traffic in exchange for cash-equivalents. They're obviously ripe for abuse, and surely the ads have terrible clickthrough rates.