Much has been said about the rise of online and mobile banking, and while buying your morning coffee with your mobile phone or managing your bank account over the Internet may be more convenient than the old way of doing things, visions of a cashless society are probably missing the point. Even if smartphone apps and chip-enabled credit cards seem like they can take care of anything we want to do with our money, there are plenty of reasons why people will always need cash - and it's not just to buy drugs. MainStreet consulted Philip Graves, a consumer behavior expert and author of Consumerology: The Market Research Myth, the Truth About Consumers and the Psychology of Shopping for his thoughts on why in some cases, cash is still king. Here is what we found.