This instinct kicks in on such a low cognitive level that it's almost impossible to suppress.
This makes it very easy to leech profits from the underclasses through payday loans. The profit is made at the point that the survival instinct programs them to ignore.
This is why outright prohibition of payday loans usually has a positive impact on the financial wellbeing of the underclasses.
Unfortunately, even the middle and upper classes who struggle with giving up smoking still look down on the set of people who take payday loans, thinking that their superior intelligence and good sense is what leads them to not be suckered.
Empirical study on the effect of poverty on short term thinking:
http://www.theatlantic.com/business/archive/2013/11/your-bra...
Study on the effect of banning payday loans on the financial health of the underclasses:
http://www.federalreserve.gov/pubs/feds/2013/201381/201381pa...