RAM is only capable of storing one bit per cell. FLASH didn't really take off until MLC technology came around giving the ability to store multiple bits per ce

RAM is only capable of storing one bit per cell. FLASH didn't really take off until MLC technology came around giving the ability to store multiple bits per cell which vastly increased the density. Theoretically RAM could be built that way but it would be much slower. Every cell read/write would need to go through an ADC/DAC, and the noise is much higher due to leakage. This slowness isn't much of a problem for FLASH because its competition was spinning disks that were slow as molasses anyways.