Till they discover they can earn gift cards for app stores through Google Opinion Rewards and buy any app they want. To be fair I know a handful of adults that do this.
The more people that do surveys like Google Opinion Rewards, the less frequently each person will receive surveys and the payouts will decrease. It's nowhere close to that but the Google Play Store also isn't close to the App Store for me at least. I have like $50 from doing surveys but there were barely any apps I wanted or want on Android.