I too am developing a project with STM and they confirmed me this intention.
In my opinion, it's a number (quantity) problem.
DRAM is focused on Personal Computer and consumer electronics, so moves very high numbers, instead of SDRAM or SRAM, wich target is embedded systems, with less numbers than PC world.
(think a minute about how many PC memories are sold per day, and how many chips are there, then think at how many SRAM memories are sold per day... sure very very less!)
I agree also with Bukitoo, about costs in production of this kind of memories...
Mix them together and probably you'll have the answer!
(I have to address 16MB of memory, but the problem is the same
)
Best regards.
Sirio.