Read/write speeds for DRAM are much faster than flash (although the gap is closing and the day may soon come where computers are sold with flash storage but no

Read/write speeds for DRAM are much faster than flash (although the gap is closing and the day may soon come where computers are sold with flash storage but no DRAM, and the distinction between memory and storage is done away with). DRAM is also a much more mature technology than flash is, so more of the low-hanging fruit for improvement has already been taken advantage of.