DRAM Chiplet for L3 cache?

One of the advantages of using chiplets instead of a large monolithic chip is that you can use functionality made with different foundry technologies.
This brings up the question of why, at least so far, no one is using a DRAM chiplet (i.e. one made with a DRAM specialized technology), for the L3 cache.  ISTM that the advantage of being able to put a much higher capacity cache in the same physical size chiplet is substantial.
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  - Stephen Fuld
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