InboxDollars doesn't care to keep you as a customer because they realize most people once they reach the minimum $30 payout won't continue, because the amount of time required to earn pitiful tiny sums isn't worth it, so revoke your earnings as you reach the threshold is an intentional part of their dishonest business model. They offer no explanation and no flexibility and no reasonable business practices.
When brands want to find out what consumers think about their product and services, they turn to market research companies. Market research companies are the ones actually administering the surveys on behalf of the corporations looking for data/feedback. Think of online surveys as a type of focus group, except in this case, everything is done online.