I think only the person who develop the apps gets the profit from the ads and those who work on the app does not earn anything.
You are actually right, only the developers earn most of the money from these apps and only a handful of early adopters and the referral marketing partners earn money from these apps. The normal users only earn a fraction of the money from these apps and most of the income goes to the owner of the app itself.
With an increase in the number of smartphones in the market, there is also an increase in number of people who are searching for ways to earn money online without any prior knowledge.