The controller makes it possible to get a standard bus and a pre-installed driver and use it to access any kind of memory from any manufacturer and any technology. It's the kind of convenience that makes people buy hardware - it's the kind of thing that made SATA and USB win. The alternative is that once in a while you plug a driver into your computer and it won't work.

Besides, I don't think manufacturers want to release the best practices for using their memory.