Physical legal tender has both benefits and drawbacks. One of the major benefits is that you can use it at establishments that don't accept credit or debit, which are surprisingly frequent if you live in a big city. Some major drawbacks are that it's more difficult to trace and much easier to steal than electronic funds. Those two drawbacks are on the verge of being remedied, though, as a team of American scientists has created paper equipped with RFID tags, making any paper money easily traceable.