Intel made a conscious decision to keep the memory controller on the chipset, which has the advantage of flexibility with newer memory standards.
This may have an element of truth in it except one not-so-minor-point. New chipsets and new processors from Intel don't work with the old ones so they are always having to introduce a new chipset and a new processor at the same time.
Its not as though the processor is remaining the same and a new chipset comes along to allow exisiting processors to work with some new memory standard.
I have given up trying to follow Intel's product lines. Its a full time job just understanding what they are selling.