In addition to what everyone has already said, memory controllers are relatively big and expensive. System integrators often ship systems <~$1000 with only a si

In addition to what everyone has already said, memory controllers are relatively big and expensive. System integrators often ship systems <~$1000 with only a single channel of memory. It’d probably be like pulling teeth to get them to actually ship a 4-channel configuration. Putting in unused memory controllers is a big waste. People who have many threaded workloads which can actually use all that memory bandwidth tend to get workstation or server platforms.