Having no DRAM means less complex pcb, smaller/simpler flash controller, lower power draw (especially in idle) and overall lower cost (most noticebly on smaller capacities).
WD 5TB My Passport Ultra now have petty prices - only 129.99$ for 5TB portable external hard drive.
5TB Mac Silver version - 129.99$
Here is 10TB external eard drive only 199.99$
WD My Book Desktop external hard drive 10TB - 199.99$