Simplir, they are not aware that their data can be used for crime in the future, they only see short -term benefits without being able to see long -term risks.
The long term risk really isn't worth the $50 they receive.
There's big fat chance that the datas will be used for something, they aren't giving free money for nothing.
Just imagine if there's data leak and our retina scan is floating on the internet can be used by bad actor to do something that breaks the law.