Companies like Amazon and Starbucks want to kill cash -- and it could be a huge blow to the most vulnerable Americans (SBUX, AMZN)

AP/Elaine Thompson Companies like Starbucks and Amazon are testing stores that do not accept cash. Going cashless can provide key advantages for retailers, such as boosting efficiency and preventing robberies. However, for the 7% of Americans without a bank account, a cashless society would mean complete exclusion. The US could be on its way to a cash-free economy. And, while going cashless has some distinct upsides in the tech-obsessed world of retail, it could be a dangerous development for so...