This question is easy to answer.  First fact; historically low interest rates do not only affect consumers; they affect banks and businesses as well, in the form of lower returns.   Additionally, typical bank profit centers such as overdraft fees have been curtailed by federal regulation.  So, the banks have to look other places for profits.

That place/those people are the underbanked.  Some financial institutions (banks and otherwise) do it through payday loans or cash advances.  But many are expanding their product line to include pre-paid debit cards. 
Technology is making the search for this target market an easier task.  Financial services companies use transaction tracking and other analyses of consumer banking habits to find persons who will be a fit for their products.  And yes, some companies are examining the social media habits of consumers to complete the picture of a potential customer.

The example goes something like this.  By examining the shopping habits of a consumer you can determine the better of possible credit risks.  Does the consumer spend their extra money at the track or do they spend it on gas?

These programs are not only helping companies to recruit new customers, but also help the “underbanked” to find sources of lending and financial services.

For more information go to:  http://www.americanbanker.com/btn/25_6/mobile-data-analysis-help-reach-underbanked-consumers-1049579-1.html