In addition to usually being faster than forms of mass storage such as a hard disk drive, volatility can protect sensitive information, as it becomes unavailable on power-down.
DRAM stores each bit of information in a different capacitor within the integrated circuit.
DRAM chips need just one single capacitor and one transistor to store each bit of information.
SRAM does not need continuous electrical refreshes, but it still requires constant current to sustain the difference in voltage.
As a result, SRAM is unable to accomplish the storage capabilities of the DRAM family.